I've played most of them..
Megaman Legends (N64)
Megaman Battle Network 1, 2, 3 (white version), 4 (red sun), 5 (dual team NDS) and 6 (gregar)
Megaman Zero 1, 2, 3, 4 (GBA)
Megaman ZX and ZX Advent (NDS)
Megaman Starforce 1 and 2 (NDS)
Megaman Battle Chip Challenge (GBA)
In other words, most MM games
Well, its a series that I, personally, adore..
The plot is usually awesome, the gameplay, the soundtrack, the graphics aint bad..
If you guys play any of them, you'll like it ^^