I love them all. But the search for the sercret levels in Crash 2 will be always one of my favourites. Let me just not start with how many hours I spent playing CTR too. The struggle of me and my friends trying to unlock the final boss (to play him) and only after years to finally read on the internet that it's not possible.
Crash Bash is awesome too but it's not made by Naughty Dog.