I gotta admit I really hate most of these intros I am watching. Sorry xD
For my favorite anime song, I probably choose the first faiytail opening song."Snow Fairy" here is the full version (not the animated intro)


It really is a song with a good mix of emotions and the translation words are pretty too. It represents the anime pretty well imo especially for it starting out.

Some others I like
he first and fourth for Fullmetal Alchemist: Brotherhood


Angel Beats opening