Many people often crown OoT as the best game ever. In my opinion I think its a bit hyped and there has to be another game on par with OoT. GTA San Andreas?
As much as I like OoT and I still don't get bored with it, I'd say another game similar to it would be ALTTP. That is one huge game!
The other Zelda games are great. The best game I found for the Gameboy was Link's Awakening. I finished that game like 5 times. Great game!