Both Mega Man and Mega Man X collections are worth owning and so much cheaper for PS2 than buying the individual games. Thankfully the emulation is done well on the majority of games on both compilations, well if you don't count MM7 and MM8.
It is sad for me to see that the SEGA and SNK collections didn't get enough care emulation wise. I often read people complaining about sound quality especially on Genesis collections, no wonder that console's music gets more bad reputation in retrospect. Digital Eclipse's port of Castlevania: Symphony of the Night to the Xbox 360 Live Arcade has some minor graphical scaling/stretching issues as well as slightly downgraded audio quality, when I compared it directly to my PS1 game.
Good thing the Monster Land collection on Xbox 360 is done excellent. I can't thank you (GameSack and PCEFX forum members) enough for having me recommended a gem like Monster World IV some months ago. Even my girlfriend thinks Asha and her blue Pepelogoo are damn cute.
Now, if the Xbox 360 controller's D-Pad won't suck so much... good thing I have an adaptor that let me use PlayStation and Dualshock 1/2 controllers, that's so much better on so many 2D games. It processes the input signals lag-free, but it needs a wired Xbox 360 controller connected for authorization though:
http://www.dx.com/en/p/ps2-to-xbox-360-controller-adapter-cable-33241#.VYbx10OhstQ