Legend of Zelda: Ocarina of Time is probably the best ever, I mean that game was so fucking fun and still is to this day, the story was just brilliant.
Golden Eye 007 basically started the FPS craze for console gaming and was fantastic, and was the start of screen peaking wars with your buddies haha.
for me the best of all time is Call of Duty 4....it was the first of the call of duty franchise to be Modern Warfare and it took call of duty to an entire different level, unfortunately I have been disappointed with the new installments of it but that is to be expected, its the same with Halo.
In a way this is hard to judge because opinions will vary over generations of gamers, 20 years from now, Halo/CoD will be complete memories, and there will be new titles that are better, hopefully virtual reality gaming where its like we are actually in call of duty.