I'm not sure what "best games" you're referring to, but consider Super Mario Galaxy... Twilight Princess... Metroid Prime 3... WarioWare. Now if you don't really go for the Nintendo franchises, well there's Resident Evil 4 (you can actually shoot things instead of screwing with a cursor!)... Godfather... hell, even Madden has Wii-specific controls.
And don't forget your history, either. A lot of hugely popular systems were around for a year or three before they really started seeing their share of great games. Take the DS for a recent example. How long was it around before developers truly started to figure out how to use it effectively? Until not too long ago I remember hearing strikingly similar statements comparing the GBA and DS.
I hardly think we've seen the beginning of what the Wii can do. Once they really get a firm foothold on what the system is capable of, I think we'll start seeing some truly phenomenal stuff come out for it.