which character is the best tank? i like using sten most of the time, but should i be using alistar or shale instead? are they better than sten at tanking?

I haven't used Shale, but Alistair is pretty awesome if you spec him right.

I always use shale. Only recently have i been using alistair, and hes okay. i think shale is stronger, but with alistair you can give him better armour and weapons

Sten + Indomitable + Intimidate (whatever the one is that pulls people away with every attack) + Taunt = rape.  You're fine.

" Sten + Indomitable + Intimidate (whatever the one is that pulls people away with every attack) + Taunt = rape.  You're fine. "

I can't imagine using Sten with a tank unless you're playing on Easy - Alistair is tough enough to keep alive on Nightmare as a mage PC, and when I played with my PC as a tank, even he with all the extra stats from the tower was squishy early on.  Pretty beast by the end-game though, played on Normal.

Either is fine.
Shale can be better in the beginning and he has better agro control, but his utility skills require him not to be tanking.
Alistair is weaker at first, but later on he is insanely tough more so then Shale and also offers some good buffs and utility while tanking.
Sten is a weird choice becouse he already has spent skills in 2h.

For me I specced Alistair completley on Shields, and making Sten a two handed, hard hitting basterd.
However, this meant I saw Alistair acting as a warrior, and not as a Templar since I did not enhance any of his templar skills.
 
Maybe a second playthr.... oh wait, theres Mass Effect 2 waiting already...
 
bastards!

Shale definitely made tanking easier.  Alistair is a good character and can be made into a successful tank, but Shale requires less of an investment...
 
As a side note, she will not spend a majority of her time hitting on your female rogue awkwardly like Alistair does... >.>

Shale is mindnumbingly good for a tank. 
 
Also I'm using Sten as a dualwielder for fun and.. he can kick some serious ass even with dual blades.

My guy.

Alistair - Give him all of the shield upgrades, use them properly, toss a regen and a lifeward on him just to be certain in a nasty situation, and he isn't going anywhere.

Shale is a good tank until enemies start getting scattershot.  Then you definitely want someone with a shield.

Definitely Alistair if you can get the high-end gear for him.

" My guy. "

Shale is the best tank, i think its better for sten to be a two handed weapon guy.

I use myself, but Shale is fucking awesome.

I tried using Sten, and felt he worked better as a melee dps with his 2-handed weapons, while I spec'd Alistair strong in shields and was surprised how well he performed under the pressure.  I needed to abandon a lot of his other abilities and go heavy into strength and constitution so that he can use the better armors.  I haven't played a warrior yet, so that might be a way to go on some play through.