Just finished gen 2. I enjoyed it overall, but I've got some beefs. Stemming from how the games were obviously designed as sequels to gen 1 first and new Pokemon games second.

>half of the new Pokemon are ridiculously rare, many are locked to the postgame, such as Houndour, Slugma, Misdreavus, Sneasel (except for in Crystal), Qwilfish, Remoraid (unless you're lucky enough to get a swarm for these last two)
>difficulty is inconsistent - Elite Four is challenging, entirety of Kanto is a cakewalk, Red is challenging again
>not much reason to play each version - RGBY encounter tables differed much more from game to game, RSE onward limited box legendaries to their games (ignoring third versions)
>time of day actually annoyed the shit out of me - barely anything is available in the mornings, but the things that are are only available then are *only* available then

I liked a lot of the additions though. I never got to use a Dark or Steel type, but they were fun to fight. I actually, amazingly, enjoyed headbutting trees and roaming Pokemon the most. Looking forward to gen 3 now.