Everybody always says that New Vegas is Obsidian's best game, or only good game, whatever. It seems to be the prevailing opinion. But I didn't even like New Vegas much, and I love a bunch of Obsidian's other games, so I guess I'm a weirdo.
Here's my favorite Obsidian games in descending order:
1. Alpha Protocol 2. Tyranny 3. Neverwinter Nights 2 (and expansions, especially Mask of the Betrayer) 4. The Outer Worlds 5. Pillars of Eternity 2 6. Pillars of Eternity 7. New Vegas, I guess
The first two, especially, are among my favorite games of all time.
Fairly similar to how I would rank them I guess. I am not really a fan of anything science fiction or futuristic however, so in my case I would exclude Alpha Protocol, The Outer Worlds and New Vegas from the list, because I blanket dislike the genre they fall into regardless (it would also make me a really poor judge of them anyhow). Tyranny I think is the best out of the remaining ones on that list, it was criminally short however and felt like a lost opportunity for something truly great. After that, NWN 2, then between Pillars 1 and 2 I am not really sure where I would rank them. I did not enjoy the story in either game, although I liked the story in the 2nd pillars even less than the first. The combat felt a bit better in the first game, however the character building in the 2nd had a higher degree of depth. I am not sure what it was about the 2nd game, but something about the combat made everything feel super spongy. There were quite a few fights where I started becoming bored during the fight, because they dragged on and on and were just a case of repeating the same button presses over and over again.