I've never rushed to finish the Main Quest - it's kind of a back burner thing in my games. However, I have a friend who played a pure mage (all perks in Destruction, all leveling increases spent on Magicka) and she defeated Alduin at level 19. That seems pretty quick to me (total magicka only at 290) but is it? What's the lowest level at which you've finished the MQ?

Level 10 on Apprentice

That was on my very first playthrough, though. Current playthrough, I was about level 20. IMHO, the MQ is not very long so I think low level characters finishing up is a norm. May be different with higher difficulty.

level 17 on my first

level 30 on my second because i didnt care.

I had a character that completed the Civil War and Main Quest at level 13, with a Mod added Weapon. I had another character at level 10 that focused mainly on the Main Quest and did a few sidequests. I do have a character at level 6 that just needs to visit High Hrothgar that might be able to finish the Main Quest at level 7, but I hate Season Unending at this point.

Still haven't finished the main quest.

Level 8. I didnt want to start dawnguard so I wouldnt level up anymore.

Hmm, I didn't consider the difficulty level. I'm not sure what she played at but I'll assume it was the default Adept level. This was before Legendary was available. Wow, some folks have done it by level 10, impressive.

Oblivion's MQ I have done at level 5 But of course, that was on easy and I was rushing things. There was also some moments I forgot to sleep so I can level up which would mean I would of been level 7 or 8 at the time.

Wow - so are you being over-run by dragons? I started the main quest and then abandoned it during my first playthrough. Once multiple dragons began to appear every time I FT'd to a destination (and promptly killed the PC, the horse, a bunch of NPCs) I decided I better go back and deal with it.

Did you just postpone the main quest? If so, how do you like playing without Shouts? I've postponed the MQ to see what it's like without Shouts. It really made me appreciate the power of the Dragonborn once I went back and picked up the MQ and kicked off the dragon soul/shout/word wall aspect of the game.

I progressed to different point of the MQ with different characters. It's just more fun for me knowing that it's still out there to complete. I have many characters that don't use any shouts or haven't even done Bleak Falls Barrow, and some characters that have tons of shouts. The dragons haven't really been a pain for me yet.

My lowest was 14 on adept. Next lowest was 30 something =P