My focus is current-gen, there's plenty of obscure and quirky titles to chase, as well as noughties/nineties PC CD-ROMs (available for a song).
I'm pretty much done with 360/PS3/Wii, only a few stragglers left for those (like I lost my copy of Shadow of the Damned). The PS2 era is similar, probably a few more PS2 games (but they're increasingly getting the very hard to get titles which never appear in CEX) and if the chance arose things like Fire Emblem for the GC. Apart from that, any interesting looking PS1 games would be a bonus. Older systems are no longer of much interest in terms of acquiring them, if I ever get the chance to get some cheap or trade for them at a good rate then fine, but I've dialled it right down, they're not available any more.