One thing you can try to do is pretend that all the games you have are a "collection."
Yeah, see that's just where it starts. A few years back I started picking up a few games because I wanted to try out a campaign or two. Of course, getting my group to try new games often felt like pulling teeth. So my "collection" began...
Of course now i've resigned myself to never playing many (if not all) of the the new games I pick up and so my collection grows. It doesn't help that a few members of my group are resistant to changing the rules they play by. Every once in a while I can convince them to try something new (just started to broaden our horizons into Midnight and M&M) but at this point its safe to say that anything non-d20 will likely remain safely entombed within my sagging bookshelf.