Anyone else do stuff like this (disliking ourselves for it as we do it)...or is it just me?!@
Generally, I don't pick up things to keep them sealed. I buy them open them and enjoy them myself and usually don't worry about it affecting it's value. Right now, the only game I have bought new that is still sealed, is Golden Sun: Dark Dawn. But that's only because I haven't had time to finish GS and GS:LA.
I do have some sealed Saturn games, a Castlevania - NES Classics for GBA, and a Naruto game for PS2 that are all still sealed. I was tempted to crack open the copy of D that I got from Foxhack, but have since decided to leave it sealed.
A lot of things I open up so I can scan the discs/carts for the site, which I suppose I make a priority over future value. Plus I've said before that most everything I own won't be given/traded/sold off until I am old and grey and ready to pass it to my kids or to other collectors.