Another shortie: Blackwell unbound
I liked the first Blackwell game, it had some minor flaws, but was overall a really enjoyable game. Unbound fixes most of these issues (apart from the fact that it was too short. I want more! (Oh wait, I have the next part in the series as well!)), and it was an awesome little adventure game.
FYI Convergence is also short - took me 3 hours like Legacy, more than the 2 hours of Unbound.
The 4th game, Deception, if you decide to get it (25% off right now) , is longer: 5-6 hours, and the ending hints of EPIC things to come in the next installment - whenever that one shows up. The character sprites, unfortunately, are worse than before (Rosa looks just plain bad IMO) but the music is incredible.