I started out really late in Game #3, the game was 70% complete when I joined, and I still managed to control 2/3rds of all passenger traffic through Seattle-Tacoma by the end. I didn't get the exact planes I wanted, the queues for new planes were measured in the years (even longer than the game would run), but I still forced the existing large and very experienced companies that were in SEA into bankruptcy.
I don't know what my final rankings were, but less than 2 years from the start, I was already in the Top 20 in just about everything. I doubt I finished that high though, as I didn't pay much attention the last few months because all my planes were due for replacement and I didn't feel like taking the time it takes to manually remove and replace dozens of aircraft on routes.
You've got to really know how to "game the game" to stay solidly in the Top 10 or so. But it's not even remotely difficult to be successful in this game, as long as you don't set your sights on #1 your first few games.