i know the ps2 can do this,but im pretty sure the xbox can,too...(need input from xbox owners)
on the ps2,IINM the console is connected using i-Link(IINM)
the PSX had this,too...but i think only 1 game used it  
point blank?
both consoles can be hooked up to the plasma/projector.
guncon with kickback isnt available for either console,AFAIK.
the only guncon available for the ps2(i dont recall xbox having a guncon) is GunCon2,and it has NO KICKBACK function
instead,it has a dpad(located at the back of the gun) and extra buttons on the side.
The GunCon for the psx,however,has the kickback function.
im not sure of the unofficial guns,but my old GunCon needs an extra power adapter to enable the kickback.
cool,but abit troublesome sometimes...too many wires

btw,the GC2 also has NO step pedal
i think Time Crisis allows you to use the secondary port of the ps2 console to enable the second controller to act as a step pedal(press any button with your feet)
i think both have their joysticks..
as for the fighting games,some of them i think are PSX titles..

anyway,i think a SF compilation was released a few weeks ago or something..
use emulators..
i heard the xbox can play them,but not sure of the ps2

The I-link is just a firewire cable that plugs into both PS2s (only the FAT PS2 IINM). You link the two together, connect each PS2 to a separate TV and voila, you can play link games.

Bear in mind not many games actually support this as compared to the old Xbox. In THAT console the feature is called System Link and requires a short network cable to connect the two consoles.

Same for those old games you're talking about. The Xbox has better support for emulators.

If you're talking about Gunshooting games, the PS2/xbox isn't the best platform for either. It's a whole different architecture which is why you won't see a Silent Scope game/controller.

there is no guns currently for plasma, projectors and flat screen tvs (preferred tv with curves!). I've done quite a research on light guns, and the result was rather dissapointing.

(3) For playing old games, the XBOX is heaven sent. It can play virtually any old games under the sun. MAME, Sega Megadrive, SNES. N64, PSX (haven't try this as it is very troublesome - need ROM of game CD image..blah..blah blah), Gameboy Advance etc etc.

With the joystick and gamepad, it is the perfect machine to relive arcade experience using MAME.