Greenlight was a good design, but poorly implemented. It was like interviewing someone for a job. They may interview great, but the final product is they are a shit employee. There were far too many games on Greenlight that sounded absolutely amazing but in the fine print it turned out those were just projected features and not actually in the game. Hell, every single greenlight game I ever looked at always mentioned they were subject to change and the final product may not be what we saw.
I think the only game I ever voted for Greenlight was a game I had already played after I bought it off the developer's website while it was being created. Unepic was a fantastic game that brought back a lot of old NES and SNES nostalgia and was actually a really good game. The developer also made another game Ghost 1.0 which is pretty fun as well.