The board game Aliens: Bug Hunt combines dungeon crawler and tower defense mechanics to bring the frantic gunfights of Aliens into a fast and friendly game.
Hrm, totally not my type of game I'll admit. Dungeon Crawlers are a bit iffy after Gloomhaven as that raised the bar so much, and I've never been a fan of plastic-centric games in the first place.
That being said, Nemesis already provides this, in a lot of ways. And it's much smarter than just shooting aliens.
Never had a chance to play this but I researched it a bunch and I almost picked it up a couple times. Looks like a fun dice-chucking romp. It uses the tile based map reveal that Sub Terra and now Clank Catacombs has too. Sadly it seems to be out of print now and according to a BGG comment the publisher may have lost the license for this one too.
Honestly project elite is the best alien blaster game if that's what your looking for. And even Aliens: Another Glorious Day in the Corp works better with an awesome endurance deck mechanic. No need to go second hand market either if you don't want to.
Legendary Encounters: An Alien Deck Building Game is a different kind of beast but it's really cool too. The way the enemy reveal works is very thematic and the various Objectives make a great use of the Legendary enemy-river system.