I started keeping a list of games I've beaten, with notes on how throughly (for instance, how many endings & what sidequests remain) & how far through the incomplete ones are. It gave kind of a an incentive to actually finish the things, to have a tally. I'm currently at 24 beaten, with completions varying from 'everything because there isn't that much' to 'barely anything,' and of course 'everything except the Futomimi battle because I <3 'Mimi-san & Chiaki's an idiot with logic holes you could fit a few worlds through.'