Yes, you must open it. However, when I have a sealed game, I sometimes wait for a special occasion to open it. I know, that sounds lame (or incredibly nerdy!), but I actually have a lot of fun doing this. I actually do this for unsealed games as well (usually games I have never played before or beloved games I've finally re-acquired).
All I'm saying is have fun with it! Invite a friend over and have a Vigilante party!
Disclaimer: The following sentences reveal things you might not want to know about me. You have been warned.
For example, I'll have a party with my brothers / nerdy friends, the "main event" is opening a sealed "Timeball" and playing it. When I finally re-acquired Master of Monsters for Genesis, I didn't play it right away. It was an abused loose copy with no label on the cart, but it didn't matter: I knew I had to wait for my brother to visit before I would play it (he loved the game back in the day).
Part of the reason I do this is because I'm very busy. But the main reason is that I am "delaying gratification" in order to reward myself for getting stuff done (i.e. I have yet to play Kiadian 00 because I still haven't finished painting base moulding in several rooms). I denote specific games as rewards for specific tasks. Then I have nerdy parties.