Man that's hard to say. I have placed many thousands of bets over the years. I have been in and out of tune with every team about 17 times.
I remember years where I killed with certain teams. Atlanta Braves during the Greg Maddux era. San Francisco 49ers the year they won the SB with Steve Young (1994 I believe).
If I had to guess for an all-time #1, I'd go with the Atlanta Braves.
Season win total # is always way off (if I'm not mistaken they've gone over at least 6 years straight). Got them at 18/1 at the start of the 2003 playoffs also. Large.