If you ever doubt your purchase, co-relate the $$ value of the game with the hours you've put into it. For ex: $20 -> 20 hours.

Saw this as a comment on a post ages ago (can't remember who by) and thought it made quite good sense. A lot of the times you may realise that you haven't given the game an actual chance and you start playing it again and you might start enjoying it for real.

On the other hand you may have just realised it was a bad purchase and maybe you'll have better luck next time.