You treat these like retro consoles [Atari, NES, et al] and keep them for when you get the urge to play an old game.
It's also help you save on re-buying the same game multiple times.
However, with computers getting more awesome, it won't be too long [relatively speaking] before there are PS3/Xbox360 emulators, like there are with older consoles.
I went to my uncles the other day and he had a PS4 he has two TV's one 32" 1080p Toshiba and the exact same but 40". He played the latest call of Duty on the PS4 and I played it next to him on Ps3 and really couldn't differentiate the difference between the graphics the games looked almost identical? Has the PS4 got better graphics than the PS3 in real world terms they look exactly the same. Although only played call of duty on them.
haha...none of the emulators I have tried could play ratchett and clank or anything, so I gave up! :(
I'm keeping all my older consoles so in 10 years' time the Dad version of me can drag it out of the loft, plug it in and show my kid/s what REAL gaming used to be like, with "none of your fancy mind-controlled 4D holographic stuff" :p