I know that each support champion has their ups and downs, and some of 'who is the best' is determined by the rest of your group composition, but is there a 'rule of thumb' kind list?

I played a game against a REALLY good Karma the other day, and there seems to be a lot of contest between her and Janna, but I want to know how do all the others stack up, as well.

Any thoughts on this stuff?

Zilean or Janna. Kinda hands down.

Zilean or Janna.

best support goes to zilean. hands down. u cant beat his ult

Zilean, or janna

Many higher level ELO games have permanent bans on Zilean and Janna, I don't quite know how people play Janna with such ruthless efficiency but she is so powerful as a support she's earned her place as a permanent ban. As for Zilean, his ultimate itself is ban worthy as it keeps alive precious people you've spent agonizing moments focusing, and he has a very powerful skill set available to him, not to mention he can rewind his ultimate so that it is up sooner than any other champion's ultimate at higher levels. So it is cast between the two of them and it generally depends on teams. Though my personal opinion is that Zilean trumps Janna just for his ultimate.

Sona, because she's tough as nails and has outstanding damage potential. Not to mention here ult in a team fight is like my me all over birthday cake. That **** doesn't stand a chance.

Zilean or Janna like others have said. After that is Taric and Alistar.

Janna fits on almost any team comp(1 AD carry and janna will help that), however taric has uber heal, Alistar has uber stuns, Sonna has aoe ultimate that stacks well with an aoe team. Karma beefs a tanky dps so much.

depends mostly on who else is playing.

No love for Kayle