Ghostbusters/Versions

Atari 2600
The Atari 2600 version, while graphically inferior, is the most faithful to the original home computer version. You do not get to choose from among different cars (you always drive the Hearse), you start with $5000, and there are only four items that you can purchase; the PKE Detector, Ghost Bait, Ghost Vacuum, and Traps.
 * City Map: There is no detail on the blocks. Zuul is not a block in the center, but rather all of the top of the screen.  There is no Keymaster or Gatekeeper.  Four ghosts appear from the lower corners and climb up to Zuul.  Ghost Bait is laid by changing the difficulty switch when the Marshmallow Man appears.  GBHQ will flash yellow whenever you are required to return.
 * Driving: Other than the graphics, the game play is identical.
 * Capturing ghosts: Other than the graphics, the game play is identical.
 * Entering Zuul: The Marshmallow Man bounds left and right across the entire screen. You must slip two out of three Ghostbusters below his feet to win the game.

Famicom / NES
The Famicom and NES versions are probably the most significantly changed versions out of them all. For one thing, you cannot continue by entering a name and account number. You always start with $10,000, and you do not start out by choosing your vehicle and equipment. There is only one vehicle, the Hearse, and it only has four cargo spaces available. You must start out by driving to the shop where you will find a much more expanded list of items, but at substantially higher prices. This is because it's generally a lot easier to earn money in this version of the game.
 * City Map: The City Map is arranged quite similarly to the home computer versions, except that there are two added features; the Shop and the gas station. You can visit the shop at any time to buy new equipment and sell off old equipment at half the original price.  The gas station is provided because in this version of the game, your car consumes fuel.  Baiting the Stay Puff Marshmallow Man is done by pressing the B button.  There is no Keymaster or Gatekeeper.  Entrance into Zuul is based solely on the amount of money you have accumulated.  If you have reached around $15,000, you will be granted entrance, but if you go to the shop and spend enough money to lower your account to below $15,000, access will no longer be granted, so earn enough to cover what you need to buy and still be allowed in.
 * Driving: Driving has changed substantially. You are no longer alone on the road, and you must watch your fuel gauge.  Other cars will appear on the road from time to time and must be avoided or you will be penalized for collisions by losing money.  Ghosts can still be vacuumed up (assuming you have the vacuum), and they will provide you with money, a random amount of 200, 400, 800, or 1600.  You can control the speed of your car by pushing up or down.  The faster you go, the higher up the screen you end up, so you have less warning if something is about to hit you.  Your car consumes fuel at the same rate no matter how fast you go, so you essentially save fuel by driving faster, but you risk missing ghosts or hitting cars.  A cannister of fuel will appear on the road every time the meters to your next destination is divisible by 100.  Hitting the cannister will replenish a random portion of your fuel.  If you run out of fuel while driving, you will have to wait while the Ghostbusters push the car to the gas station and pay to refuel the car.  Drive to the gas station on your own, or collect cannisters to avoid having to wait.
 * Capturing ghosts: While the process is essentially the same, several details have changed. There will no longer be only one ghost.  Now there will always be four ghosts when you arrive.  The beams from the proton packs don't confine the ghosts, they literally hold them in place.  You can adjust the position of both men as much as you want before the trap is triggered.  You can even control the angle of the beams, which always start straight up, which is best to avoid crossing streams.  Once you are ready to spring the trap, the lasso flies up and down bring all ghosts with it.  The value that you collect for each ghost rises incrementally from 200, 400, 800, to 1600.  If you do not capture all of the ghosts on the first try and you still have another free trap, you can continue to attempt to capture the ghosts, but the point value will reset to 200, so you can only get 1600 points if you capture all four ghosts at once (totalling 3000 points).
 * Entering Zuul: This is the most significant change in the game, and probably one of the most hated. No longer must you slip into the building between Marshmallow Man's legs.  You can enter the building as soon as long as your bank account is over $15,000.  Once you enter, you begin on the bottom floor of a 23 story building.  Your job is to climb all the way to the top floor to fight Gozer.  However, in order to move, you must hold the direction pad in the desired direction while tapping the A button to make the Ghostbusters move one step at a time.  To prevent you from reaching the top are four ghosts that float aimlessly around the screen.  If they touch any of the three Ghostbusters, which you control simultaneously, three times, they will fall down.  If they fall down three times, the game is over.  You can purchase equipment to make this easier.  The Ghost Food can be used to distract the ghosts and pull them over to some portion of the screen, but you only get two uses.  The Anti-Ghost suit will enable you to sustain five collisions with a ghost before falling down, and at $20,000 it's quite expensive.  And the Sound Generator will slow the ghosts down, making this section only moderately easier than before, but at $100,000, it's next to impossible to purchase.  If you do manage to make it all the way up to the 23rd floor, the Ghostbusters will run through the door and you will fight Gozer.
 * Fighting Gozer: This portion of the game plays like a typical shooter. Two Ghostbusters standing side by side will shoot beams that must hit Gozer's head.  Gozer and two dog statues fire small slow beams at you.  Ghosts will appear in front of Gozer and absorb your shots.  You must keep moving in order to avoid getting hit.  If you stray too far to the bottom, the screen will scroll down and the scene will shift to the opposite side of the building where the giant Stay Puff Marshmallow Man will be climbing up the side of the building.  If you do not defeat Gozer before the Marshmallow Man reaches the top of the building, the game will be over and you will lose.  If you succeed in shooting Gozer enough times, you will be treated to the ending of the game, which features an extremely poorly translated message that reads exactly as follows: "Conglaturations!!! You have just completed a great game. You have prooved the justice of our culture. Now go and rest our heroes!"
 * Money glitch: In some versions of Ghostbusters, you can purchase and sell Ghost Alarm continuously for a profit; its purchase price is $2000, but sells for $3000 instead of half it's value. This was fixed in later revisions of the game.

Sega Master System
The conversion for the Sega Master System was only released in the United States and Europe, but not in Japan. It is faithful to the original game for the most part, but it features a number of changes that attempt to put right what the NES version got so horribly wrong. The only glaring problem with this game is the degree to which the main theme song, which plays throughout the entire game, is off-key. You do start the game choosing which car you want to buy, as well as purchasing equipment from an expanded inventory list which includes items such as Super PKE Detectors and Super Ghost Vacuums in addition to the normal variety for much more money.
 * City Map: Like the Famicom/NES version, a shop has been placed in the upper right portion of the screen, allowing you to go in and buy new items or trade old items in. This allows you to upgrade your equipment while the game is in progress.  The Keymaster and Gatekeeper are visible on the map, not as symbols, but as real people who wander the street.  In fact, hitting them with the cursor will cost you money.  Everything else is the same as the original versions.
 * Driving: Once again, like the Famicom/NES version, the driving section has been enhanced, but it considerably easier. Your car will automatically accelerate to its top speed while you remain near the bottom of the screen, making it easier to see and dodge oncoming traffic.  Ghosts can be vacuumed up as usual.  The only other obstacle that you must watch out for are construction barriers placed in front of open man-holes, which can be very difficult to dodge when your vehicle is moving at top speed.  Hitting one of these will delay the game and cost you money.
 * Capturing ghosts: Like the Famicom/NES version, there will be more than one ghost floating around the block. You can control the vertical position of each Ghostbuster as well as their horizontal position.  The beams always face upwards, so you can't cross streams.  The beams push the ghosts along better in this version than any other version, even if the beam isn't reaching all the way up to a particular ghost.  Any ghosts that escape being trapped will slime one of your men.
 * Entering Zuul: The Marshmallow Man sequence has been removed, and you must climb to the top floor of the building with at least one of the Ghostbusters. As you climb, ghosts will appear, but you are free to shoot at them with your proton pack.  You can shoot horizontally or diagonally.  If you are hit once, that Ghostbuster is removed, and another Ghostbuster must attempt to climb the stairs from the bottom floor.  Once you reach the top floor, you will fight against Gozer (who is referred to as Gorza in this game).
 * Fighting Gozer: The Gozer battle is a little more difficult in this version. Gozer will appear every now and then, firing off an array of lightning, which spreads out in a fan like pattern, but not too much to the sides.  Because of this, it is easier to attack from the sides, firing diagonally from below one of the dog statues, then to attempt an attack from head-on where it's too difficult to get out of the way of Gozer's attacks.