toshiro loses to Hailbel stark and kyoraku never really battled..
I'm pretty sure most of them do, because before they were turned into Vizards by Aizen they were Captains and Vice-Captains
To get "Lord Aizen" you need to complete and beat him in Urahara tower
By using his final attack which carried the price of his soul reaper powers.
I think it's fair to say that Aizen won against the Captains in Bleach. Considering he cut Captain Hitsugaya in half, scorched Head Captain Yamamoto and, between himself and his Arrancars, killed/maimed/injured pretty much everyone in the fake Karakura Town. Against Ichigo though, I'm pretty sure Ichigo owned him. Well, Mr. Urahara did anyway.
Hitsugaya did not beat Tōsen; it was Hisagi. This occurred in episode 291 "Desperate Struggle with Aizen! Hirako, Shikai!"
HE CAN BEAT #4 OF THE ARONCARS so he can kill all of the captains in his ultimate hollow form <cheak episode 271>
Well, I believe Ichimaru Gin is dead. At episode 308, when ichigo has arrived, he said, ur at a level, where i can 'die' and leave this to you,. And he also said, im glad i said sorry "goodbye rangiku" which really meant, he knew he would die at the end, sacrificing himself... (New Edit by random stranger) In the manga, Gin is traveling with Aizen in soul society, where they transported Karakura town (in order for Aizen to not get his hands on the souls there, but Aizen ends up getting past the Captains). Gin pretends to kill Rangiku because of Aizen's orders. Gin inserts a piece of his Zanpakutou's sword into Aizen, and destroys Aizen from the inside out, but the Hougyoku saves Aizen and he remains unharmed. Aizen kills Gin, and Rangiku finds his body, and is heartbroken.
obviosly ichigi would win he beat kenpachi byakuya ulqiorra and aizen
If your talking about Captains vs. Espada, then it hasn't ended at all yet. Not even in the Manga.
Aizen is hundreds of years old.
Taking all things into consideration, I believe that Aizen would win due to his superior experience and power. actually byakuya would win if aizen didn't have complete hypnotis as a shikai, otherwise aizen wins Kyoraku Shunsui, the 8th captain can beat Byakuya as he had beaten Starrk, the 1st espada shunsui never actually "defeated stark" he was actually defeated by stark, he wouldn't last a chance against stark seeing as he is only second best to yamamoto head general, who has the same powerlevel as aizen and he didn't even defeat aizen
Aizen is 1,050 years old