I enjoyed playing Beats of Rage which as you might have guessed, is a fan game made as a dedication to the Streets of Rage series. So if you like OpenBOR games, definitely give this one a try. Here's a video of it:https://www.youtube.com/watch?v=CACanuonT2U
The Streets of Rage remake fan game is also excellent, although it was made independently, not in OpenBOR.
If you enjoy fighting games as well, Mugen has quite a few good titles which can be modified and customized by editing various files within it. So far I've only played three which I really liked: DBZ Mugen - Edition 2011, Samurai Shodown Mugen Especial Edition and Street Fighter vs Fatal Fury. There's probably more up to date versions of these, as well as many more options to choose from as with OpenBOR.