I used this for the MMX marathon i'm doing right now. My last one was like 10 years ago, and replaying these games i noticed they're not as good as i remember.
X1 holds up perfectly and is still the best, but x2/3/4 are not that great. There's always some flaw that keeps them from being as good as X1. Weak levels, annyoing gimmicks, questionable soundtracks, etc. And this is the best the X Series has to offer, a masterpiece and 3 very ok but still fun games, the second collection has the bad ones.
I'll admit i prefer the classic series, during my classic marathon i found new things to appreciate including a new favorite in MM6. In my X marathon so far i'm only confirming what i already tought about the games (usually negative) or being disappointed by one i remember liking, including my original favorite X3.