Recently found myself going through the early Megaman games, and I feel like I get why people love them so much. They're filled to the brim with character and personality, and the Robot Masters all feel so distinct from each other. I found Heatman particularly great, essentially being just a glorified Zippo lighter.
I expect to try and tackle all 8 robot masters from Megaman 2, and I think it's quite doable given how simplistic (most) of their forms are.