I went and bought Age of Empires 3 the other day, played the first two, so thought I'd give it a go since it was only £15. Has been good enough for the price so far.
Also I tend to buy lots of games from Good Old Games, even if I've not played them before. It's easy enough since they are $5.99-$9.99, so if they aren't so good, I've not lost a lot.