They're both different enough that it depends on how you want to view the series. The original MGS was more conservative with the "off the wall" antics of its successors, and The Twin Snakes fixed that. In addition, TTS is made incredibly easy due to the addition of a first person aiming mode.. Overall though, I prefer MGS:TTS due to the graphical enhancements, new scenes, and cut dialogue (most of which was boring anyway, especially that long-ass President Baker sequence). I'd say get the GC version, skip MGS2, and wait for MGS3: Substance (Subsistanance?).