Well now I've listed the best, let's skip to the rest. (they're all awesome too though)

Someone mentioned the BBC having great opening themes...
Granada theme: Sherlock Holmes long intro - YouTube
Poirot - tv theme - YouTube

HOW ABOUT SOME TRULY OUTRAGEOUS 80S MUSIC
Jem Opening - YouTube


The 4Kids haters deny their childhood. They deny that at one point, they wanted to be the very best like no one ever was. This song is as legendary as any anime opening ever.
1st Pokémon Opening - Full Theme Song (English + Subtitles) - YouTube