I forgot to mention this before....

The thing that makes a live album great is when it sounds and "feels" like it's really live and you are there almost. A lot of so called "live" albums are anything but by the time they make it to the retail racks..

The obvious example would be Ozzy Osbourne's tribute to Randy Rhoads album. I love the album, mostly because of Randy's playing, but it isn't a live album by any means. Every note of Ozzy's vocals on that album was recorded in a studio.
How do I know this? Because I used to have a bootleg of the very same show in it's original form, and Ozzy's voice was kinda rough, some lyrics forgotten, some sang out of order, etc. All of which mysteriously vanished 7 years later when the album was finally released.

Black Sabbath's Live Evil was much the same. Ronnie James Dio sings great live in my opinion, but apparently not in his. In fact, the reason Sabbath II split up, according to Tony Iommi at the time, was that Dio was "trying to make Live Evil sound like fucking Barry Manilow". An exaggeration? Perhaps, but if you ever heard a boot of Sabbath w/Dio live, you would have to agree that the vocals on Live Evil are a bit suspicious.

My point is that a great live album is just that. It's great because it's actually LIVE, catching the band at what they do best. Save the overdubs for the studio albums, and don't throw a studio song on to the album, mix some crowd sounds in and try to bullshit the fans (i.e. about half of KISS Alive II - and no I don't mean side 4- and Van Hagar's cover of "Won't Get Fooled Again" on the RHRN "live" album. Yes it IS a studio recording, trust me.)