I actually really liked Toy Story 2. It found a key element that made TS1 so fun (Buzz having to deal with the fact that he's a toy rather than a real space hero), and allowed the same character arc to happen again in the sequel (another buzz gets unboxed).

I was hoping they'd do the same with MIB2. MIB1 had Will Smith having to come to terms with the fact that aliens were real, and they were able to do the same thing in MIB2 by having Tommy Lee Jones' memory erased. While that part of it was fun, other aspects of the sequel made it less fun than the first one.