While I like to collect them, I also like to play my games, so I break the seal every time. Admittedly, though, I still have a number of games that I haven't opened yet, but will eventually. I'm pretty sure every gamer has a game or two still sealed in their collection.
I have collected many other things in my years, but keeping video games sealed has never made sense to me. Much less grading them. To each their own, I guess.