Kinda focusing on series right now, and have been the past year or so.
Funds are a bit tight because uni expenses come first, but I'm really enjoying collecting Sonic, Simpsons, Mario and Crash games. (Original I know). It's really enjoyable to casually buy something in those series I've not got yet to play and most of the time finish.
For some reason golf games are a guilty pleasure, don't ask me why I don't know. I'm going after all the golf games for each system I own, while focusing on PS1 right now. I have 4 left to get, then one needs a manual. After that I'll move onto the PS2 ones and add the occasional one where I see the opportunity. No real rush.