I typically hear debates between people arguing whenever the Gamecube, Dreamcast, or the Sourcenext PC version. Some also will argue N64, as that version has some content that is exclusive to it.
Basically, it's cut like this:
Original PSX version is obviously the base game, so none of the later content is included with it.
There was a redone dualshock controller version of RE2 for PS1 though. This version included dualshock support, as well as a new EX Battle Minigame. Notable this is the version available on PSN.
Nintendo 64 was the worst looking and worst audio compressed version, and one cutscene in the game was cut. But the version does include a few things that weren't in any other version, which includes the ability to change blood color, extra readable files, an item randomization system you can turn on that will make where items are stored have a random item (like ammo, a herb, etc), and a cameo of the Hunter. However, the Nintendo 64 game missed the EX Battle Minigame.
First PC release is the dualshock version, but with everything unlocked from the start (EX Battle Mini Game, Tofu and HUNK scenario) and prettier looking.
Dreamcast is the PC version, except some argue its better as it was way better optimized for the Dreamcast than the PC, and is tied for best graphics with the Gamecube (better resolution on the Dreamcast, but the Gamecube version received graphic updates).
There later was a Sourcenext PC version in 2006. This one has the second best graphics and best audio, and the only version with uncompressed video, but one big notable thing is that for some reason Leon and Claire's campaigns have been combined into one large campaign
Gamecube version had everything of the Dualshock version, though the minigames were unlockable again and not unlocked from the start like the PC and Dreamcast versions. Cutscenes can be skipped in this version (can't in other versions), and a few minor changes (the 'RESIDENT EVIL 2' narrator at the start is different, end credits show CG scenes from the game), and is also tied for the best looking version (Gamecube version was updated some to look better, but Dreamcast has the best resolution).
Honestly, Gamecube or Dreamcast is the way to go, unless you want some of the quirks of the 64 version.
