Far from it, if you like TSPP you made the right choice. Don't let everyone come in hear and tell you what game is best, it's all personal. If you don't have the room or funds, I'd rather have a game I really want than one that is worth more.
I can't see myself getting rid of my EATPM, and I've been offered games at much higher value. Personally it's one of my favorite in my collection even though it is the lowest in value.