I've got a bit over 40 games for the system, but I'm still working on picking up some of what I guess would be considered the most 'basic' foundations of a PCE/Turbo collection...
I don't have any of the Tengai Makyo games yet, but they're cheap and easy to find (I do however own Tengai Makyo Shin Den/Kabuki Klash for the Neo Geo AES, go figure). I still gotta get Devil's Crush, I'm kinda holding out to find a copy for under 30 bucks, but it looks like I may have to bite and pay the going rate for that one. I'd like both Gunbuster games (2 is easy to find, 1 a little less so), and I still need Snatcher, any of the Shockman games, Rayxanbers, Spriggan, and Download.
Those are the games I'm my eye on, but I really haven't been buying Turbo/PCE stuff lately...trying to save money for some new tattoo equipment and a trip to the Pacific Northwest!