I've played almost every Mega Man game. I think the only ones I've never touched are the Wonderswan games, MMBN6, and Star Force 3.

My favorite is Mega Man ZX. I get why people hate the map system, it's a mess, and something the sequel dramatically improved. If you remember where every door goes, it is manageable, but on first playthrough finding your way around is rough.

But I love the characters, setting, general game feel, and my god, the music. That game has some of my favorite game music of all time -- especially the CD version of the soundtrack, which these days you can use with the PC version of the collection. It took all the right stuff from the Zero series, and none of the stuff I wasn't very fond of from that series.

I'm glad it feels distinct from it. I don't hate the Zero series, but it has a lot of stuff that I personally feel very frustrated by, such as the whole ranking system and the way you are discouraged from using Cyber Elves, etc.

My second favorite is Mega Man X2. I concede X1 may be the more iconic game, but I feel like X2 improved on virtually everything about it other than some boss designs. (And then X3 came along and went quantity over quality on its content...)