4th gen had the best legendary themes in my opinion. They actually made it feel you were fighting something powerful.
4th gen:
http://www.youtube.com/watch?v=6Mv8AxBTlJ0http://www.youtube.com/watch?v=c5bRPL2Hg2I (this one especially)
http://www.youtube.com/watch?v=XXsBks4HRlsThe fourth gen had GREAT opening sequences for pretty much every legendary fight; that slow buildup coupled with the WOAH EVERYTHING IS SPINNING camera thingie was tense.
>there will never be a pokemon game where all legendaries you initally encounter outlevel your team by like 20 levels