The ending is a huge part of the match, and usually the part that everyone remembers the most. Part of what makes a good match is a great ending, with good psychology. So it is definately important, and can make a match a lot worse if the ending isn't right. There can still be great matches with an ending which is bad (Mankind v Shawn Michaels at Mind Games 96 is the one that comes to mind, it ended with interference and a double DQ) However, most classic matches need a great ending which has been built up or is original.

I know exactly what you mean about Benoit/MVP. The ending just didn't seem right. It just happened so suddenly. It left a bad taste in my mouth too