I also filled a lot of notebooks growing up with fictional leagues of various sports. I'd make up schedules and roll dice to decide who won each game.
I eventually got hooked on PureStat baseball.
http://www.stadium64.com/gameinfos/p...atbaseball.htm
It didn't have a season or franchise mode, so I acted as GM for all eight teams. I did a fantasy draft, manually created a schedule, and kept track of records. I played out every game for my team, and simulate every other 3 game series. I'd print out the results of each game then type them into a computer program I wrote to keep individual stats for the entire league.
I eventually upgraded to a new computer and couldn't get PureSim to run correctly. I used Front Page Sports Baseball for a few years before that franchise folded.
Finally I found OOTP 3 and have bought every version since.