If you win 55%-57% of your games (Non-baseball for obvious reasons), you are doing very well.
If you end up with a ROI of 5%-10% you are doing very well. That number will differ year to year. For example, in the NFL last year, I had a ROI of about 8.9%. I was 65-49 and had a gain of around +30% of my bankroll (different from ROI). But that was just one year. Over the course of the last four years, my ROI in the NFL is closer to about 5-6%. In the NCAA basketball tournament, my ROI over the last four years is around 7%. I had an incredible year two years ago, where I went 44-28 and returned around 50% of my bankroll. My ROI that year was 16.7%. That's truly incredible. But it was only one year.
Anyway, if you are getting around 5-10% over the long haul, you are doing very, very well.
I think some people are answering thinking what should your return be for the year, not your ROI.
ROI. In the NFL last year, I was 65-49. Assuming I am playing into a 10% vig, and played 3% on every game (3.3% with the vig), I played a total of 114 games times the 3.3% w/vig. I risked 376.20% of bankroll. I made 11.1 units or about 33.30% of my bankroll. That 33.3% divided the amount risked 376.20 = 8.9% ROI.
So you can see, even in a good year, there is no way to achieve 75% or 200% like some people have answered. I think they just confused ROI with your yearly return of bankroll.
I also think you are probably right when you say it should match the books return. That seems like a pretty good goal.