Wow...I just got RE4 for the PS2 and it kicked my ass all over the place! This gem rejuvanted the series that I once loved, and now its back better then ever. I love everything about this game and how much it improved from the previous installment. Its all in 3D now with the best control yet in a RE game(those stiff controls of old are gone!). It uses a totally diffrent engine for its gameplay mechanics, and it does the job well. It basically borrows from the play mechanics of DMC3...even the interface and weapon upgrading are similar in style. The atmosphere is also great, with its true wide screen format that makes the cinematics/cut-scene rival the best stuff from Kojima, but its not as long which maybe a good thing for some people. The biggest improvement besides the graphics are that the enemy AI isn't dumb anymore. Once they spot you, they call up their partners and gang up on you. Once I've tried hiding in a shelter to shoot them through the holes on the wall, they kicked down the door in packs! I'm not sure what's the difference is between the PS2 and the GCN version other then the progressive scan support for wide screen and more options. I guess you could debate that the GCN version has a more polish graphics, but my brother who owns the GCN version couldn't tell the difference unless your're using a HDTV. This game is defintely my top 10 of all times and could possibly be nominated for GOTY. Highly recommended for action horror fans, or those who enjoy the DMC series.
Yeah, the PS2 version is almost identical to the GCN version graphically. It has a few flaws that are apparent if you look for them, but otherwise, the game looks just as good from what I could tell. Capcom did an excellent job porting it to the PS2. Other than the graphics and option, I believe the PS2 version has a few more bonus missions/features, IIRC, than the original GCN version. For the RE fans, it would probably be enough to get the PS2 version even if you already have the GCN version.
I just rented The Warriors and it was really fun. At least, it's really fun if beating hundreds of cops and gang members to death sounds like your idea of a great game (it should). The first half of the game is basically backstory where you build The Warriors' rep and then for the second half you basically play the movie. The brawls are great, but there is also plenty of sneaking around and goal-oriented levels, too.