I think games that are set up too easy are boring. Some DMD-gottliebs are boring on default settings but are fun when set on 'hard' (software) and steep enough. Same goes for a lot of Stern-DMDs or (Alpha)Numeric games.
A boring game (after a while) is Road Kings: though I like the layout, I like the sound and lights and I like the rules, it's just too easy to beat and therefor too repetitive! Because I really liked the layout and opportunities, it became my first P-ROC project .
That said, maybe it's quite a fun game on original software, steep enough and set on 2 balls (or 3 and no extra balls).
I really like LOTR as a total package, but after a game of almost an hour in a bar, I didn't really want to go back. If I'd own one, I think I'd set it to hard with outlanes open and such, even though that'd mean that I wouldn't get very far in the rules.
I own a Stargate. Did like it a bit at first, started to get a bit less fun, put it on harder settings and I really love that game now.
Ok, what was I saying again? Oh yeah... it's important to me that a game isn't too easy.