Someone said to start with Air Man? No way, start with Metal Man. Easiest robot master and also gives you the most overpowered weapon. But you're definitely outlying some of the big problems I had with Megaman 2, and why I can't understand how it's loved more than any other game in the series. I actually wrote up a big rant about it, outlining nearly all (if not all) of my reasons for disliking it.

If you're disliking Megaman 2 this much, you'll probably be like me and enjoy 3 a lot for the sheer reason that it's not 2. 3 isn't perfect and it has some areas where an eyebrow or two can be raised, but it's definitely a lot more well-done (though if you ask me, 4 is the most polished of the NES series, even if it's somewhat lackluster in the music department). Top Man or Magnet Man are my recommendation for starting with, I'd say Top Man is the easiest to buster-only, but Magnet Man is pretty simple too.