Yeah, if you play X-2 first you're jsut gonna be lost. Horribly, terribly lost, throughout a GOOD chunks of the game. And it depends on your skill level, and how much you delve into the game (FFX)
You can get TO the final dungeon in thirty hours or so, if your fairly skiled, but to do all the sidequests and truely enjoy the game, set aside 80 or so hours, maybe as much as 100. all in all, you get a $20 that goes for 100 hours. Thats like 20cents an hour. try to find that kinda bang for your buck elsewhere.