While I think MGS3 is the best MGS, on any given day, I'd prefer to replay MGS2 over MGS3. MGS3 is too long, and due to the lack of radar too tedious to replay. Your ass is in the grass half the game. MGS4, although it sucked balls, did well on that note: the perfect balance between no radar and not making the game tedious.
I could replay MGS2 multiple times if asked, however. Hell, I replayed tanker chapter eleven billion times, trying to beat it in 10 minutes and shit.