That awesome-looking mod for GZDoom that combines the best parts of Aliens: The Ultimate Doom with Alien Trilogy? Creator Kontra Kommando has released a beta you can play right now.
The 125MB modification is essentially Ultimate Doom, but juiced with new visuals:
...using the original Alien Trilogy graphics, I have created new rotation attack frames, blood and gore sprites. This mod takes the aesthetics of Alien Trilogy, and combines it with the action and game play of Aliens the Ultimate Doom. Special thanks to Lex Safanov for decompressing the Alien Trilogy files!
For a beta, it's already slick, though comments on the ModDB page suggest the aliens might be too fast. Not that they've ever played fair...