Comparing MIB to Buzz isn't exactly fair.
On the surface, they are similar rides.
However, Buzz Lightyear was designed as a replacement, to fit over an existing attraction. On the other hand, MiB is a completely new attraction built from the ground up. One is essentially an upgrade to a ride, while the other is an upgrate to a park.
When you consider that important factiod, I'd easily say that Buzz kills MiB. While MiB does innovate the ride genre slightly and it presents some imaginative concepts (the other car as aliens is a riot) it doesn't give the same bang for the buck (ride installation and size of ride) as Buzz. Since both rides offer the same re-ridability and the same basic entertainment value, Buzz wins because it produced the same result for much less effort.
Do both rides innovate the theme park market? Yes
Do both rides off an exceptionally high degree of re-ridability? You better believe it
Are both rides fun? Of course
Both rides are winners in my book. I'd easily wait for an hour to ride each of them.