Question is, how many of those games are you still playing?
I have a few PS3 games (maybe 5), GT5's 10GB install will still fit on my 40GB HDD without having to delete something else.
I still have a 20GB HDD on my xbox360. I have loads of games... but the ones i still play now and then i can count on one hand. What really takes up space is DLC for all those games. However, i simply delete the stuff from the games i don't play anymore... and if i ever decide to play them again, i can simply re-download the DLC (without having to pay again).
I also download demos and arcade games. Same here, don't play it anymore, delete it.
In other words, i don't see the need for more HD space on my consoles.