Correct opinions stated in this thread-
-BTTF2 is the best them, despite the silliness of changing the future that hasn't happened yet, especially after the future is apparently entirely wiped according to the end of part 3.
-Claudia Wells >>>>>>>>>>>>>>>> Elisabeth Shue in those movies. Not even a comparison there between super hotty and dorky plainness. However, I'd say that Claudia Wells has aged badly, and Elisabeth Shue has aged really well, so as of 2013 Elisabeth Shue looks much better.
It really comes down to the fact that they never wrote BTTF with a sequel in mind. I guess once it's established, you kind of have to work with it. Luckily it made for my favourite movie scene of all time, so I don't care!