The new multi-player options and superb gameplay could actually keep you playing until MGS 2 in October. I've played precious few PS2 titles that are better, and Winback is certainly one of those games that will seem impossible to put down.
This is a pretty good cake, albeit of a flavor you've probably never tried...I'd put Winback ahead of "X-Squad," on the strength of its better-thought-out gameplay and far longer mission (not to mention the replay value all the multiplayer modes add).
Compared with the sights/sounds/gameplay of "MGS2", the technical flaws that were present on the N64 version (and haven't been fixed in this PS2 port) stand-out like a sore thumb on Roger Ebert's hand (there's a lovely image for you!).