I disagree. While I consider MMX2 the weakest of the first four games (it's awesome compared to the trash that follow X4, though), the first X game is one of my favorite Mega Man games of all time. Only the first 3 NES games come close.
Ranking the games in the collection: X > X3 > X4 > Battle & Chase > X2 > X5 > X6
The readers post their own reviews.