Well, here's a selection of classic intro songs sung live!
First, Ichiro Mizuki singing the Mazinger Z theme and being awesome:
Now, a truly energetic performance by Hironobu Kageyama singing "Cha-La Head-Cha-La", the immortal intro theme to Dragon Ball Z:
Let's get some Doraemon action going with Satoko Yamano singing her intro for the show (the one after Kumiko Osugi's original):
Time to step things up a notch with Make-Up's classic Saint Seya theme:
Another memorable one you might recall is Yoko Takahashi's theme for Neon Genesis Evangelion:
And, to end things with a bang, here's Gundam Wing's intro song "Just Communication" by Two-Mix:
Any more to recommend or any specific ones you'd like me to post?
Let us know in the comments below ;)