Ya know, there are some songs where the live version is just so much better than the studio. Whether it's because I heard the live version first, and then it just made the studio version painful, or whether the live version truly is superior to the studio version.
Witch Hunt (A Show of Hands). I heard this version before I ever heard the studio, and I just love the electronic drum fills Peart lays down.
Closer to the Heart (Different Stages). The jam session at the end puts all other versions to shame.
Freebird (Gold & Platinum). 14 minutes of Freebird > 9 minutes of Freebird
Rock 'n' Roll All Nite (Alive) - The staple in Kiss' extensive live repertoire. The guitar solo is so much better live
There's Only One Way to Rock (Right Here Right Now) - Van Halen makes this so much more rockin than Haggar could by himself
Hollow Years (Live at Budokan). Two words ... Guitar Solo
Octavarium (Score). The studio is a 10/10 for me, but add in an extended intro, orchestra, the Octavarium animation, JLB's awesome scream, and the visual of JP's bear roar at the end of the solo... it's better than perfection.
That's all that come to mind right away, I'm sure I'll come up with more later. What else?