To be honest, while I agree with you on those other games, I have to side with him about OoT. Mostly, at least. It absolutely is a good game, but practically everything in it has been surpassed in quality by the following Zelda games. Calling it the "best game ever made" (a claim which occurs more with OoT than with any other game I've ever seen) obviously smells like fond childhood memories, rather than an honest summation of its merits.
Playstation fans from the same time period will say the same thing about FFVII, but as much as I love the game (I rank it as one of my overall favorites) I don't agree with them either.
Calling either of them overrated might be an exaggeration (since they deserve the ratings they've gotten, for sure), but they certainly could be called overappreciated. "Quality" is an ever-changing concept, so branding anything as "the best ever" ought to be a fleeting sentiment. I'll find myself saying it every now and then about one thing or another, but I always regret it afterward, because it feels like too much of an all-encompassing exaggeration.