I'll buy a sealed game if possible every time, but I open them always. I admit they sometimes sit sealed on my shelf until I'm ready to play them. But having everything in nice new condition is great, because I know I'll take care of it. The used game market can be so depressing with all the messed up cartridge stickers, children's names scrawled in marker (or worse, see pic below), missing manuals, missing other stuff like posters, etc. See my recent unboxing of Cosmotank, my mom found for me for Xmas. Pretty cool to open a new GB game, got a poster which I'm gonna frame and hang up for cool game room decor. I've already played it a couple times and I know it will stay in nice condition for as long as the sands of time will let it. I just think keeping games sealed is a shame. Of course you can emulate in many cases, but one thing I've found is with an unlimited pool of free games, you tend not to want to play any of them. If you carefully acquire just the ones you really want one at a time, you will give them a little more love and attention.
I think everyone here is aware of the supply and demand issue concerning classic games. There's a finite supply and keeping games sealed or worse (VGA graded) relegates them to the status of currency, functionally no different than a $50 or $100 bill, to be passed around and fetishized but never actually used for it's intended purpose. It's a free market though, and if you buy em' sealed, you're free to display them that way. I do think there's a degree of fetishism no matter what, I basically described that above. But get the full use out of your purchase! It can still be kept in nice condition after opening it. And emulation isn't the answer for everything. NEC emulation is pretty good, but I'm sure a few people could point out weird issues with certain games. Saturn emulation blows. N64 emulation blows. Just sayin'.