You know what else sucks? Correct me if I'm wrong but deleting a game also deletes save files. Lame...
It only deletes Vita game save files. If you delete PS1 and PSP games, the save files still stay on your memory card.
I have about 37 games installed on my Vita now, but I honestly don't know why. I only play one or two out of that 37 at any given time. When I complete a game, I delete it, as I probably won't be going back to it for a while.
I've only downloaded the ones on there now because I can, but I'm about to start trimming them away again. Some, are permanent fixtures, that I'll never delete (like Castlevania: SOTN, Chrono Trigger/Cross, etc), but most are expendable. You have to ask yourself, and be reasonable about it: "Do I
really need 'XXX' on my Vita at this moment in time? Am I actually playing it, or actively playing it right now?"
If it's a game that you play more than twice a week, keep it on your system. If it's a game that you haven't touched in months, just delete it, and redownload it later when you actually want to play it.
That's worked for me in the time I've had my Vita, and upgrading to a 32GB card seems like less of the worthwhile investment I thought it was now. I still have 10 gigs free.