Originally Posted by darkling
Says the guy who releases essentially the same game every year.

But that's his point. He can do that because his engine allows to tell a relatively wide range of stories and can create a varied range of scenarios that work for a number of games. I don't know his games well enough to judge whether his incremental engine upgrades have really expanded the gameplay elements over time.
I also think that the Legend of Grimrock engine could be upgraded in a number of ways that would allow an increase its design space (e.g. with a solid dialog system).