Are you kidding? The third title in their famous Baldur's Gate series just came out and everyone is talking about it. It's being called a triumph of PC gaming and a return to form.
Oh wait. They only made the first two. (The answer to your question is ME1)
Mass effect 2 was much more polished, even if it did lean more towards action than RPG. I personally didn't like Dragon Age inquisition, but it was widely acclaimed and was the company's most successful launch at the time.
You might also be thinking about Planescape Torment, which was developed by BlackIsle with licensed BioWare technology (the Baldur's Gate engine). As far as I'm aware, Planescape Torment is the closest BioWare has ever gotten to the creation of an excellent game.
BioWare developed the Infinity Engine, BG1 and BG2. Interplay was the publisher. Black Isle was an internal division of Interplay and box label. Black Isle developed Icewind Dale 1 & 2, and Planescape: Torment using the Infinity Engine.
No, I got the joke. I'm fully aware that Baldur's Gate 3 is not related to Bioware at all.
Also that Larian is basically eating Bioware's lunch right now because Bioware has dropped the ball on Dragon Age which would occupy a similar space to BG3
It's actually even funnier that Larian is doing it by using a franchise that Bioware built 20 years ago.
But generally I think many people who love these games are in it for the writing, the character romances, the storyline, and the exploration. In this regard, Baldur's Gate 3 has a lot of similarities with Dragon Age 2 and Inquisition, and presumably Dreadwolf whenever that comes out.
The individual details of the mechanics are less important to many.
You should play Dragon Age: Origins. It's a lot tighter, way less filler. I look at these games with a million copy-paste quest markers and "points of interest" and just know there's little actual substance there.
Or you can play Baldur's Gate 3 like everyone else is now :) The DnD systems take a bit of getting used to. The game is an excellent story-telling experience, despite that ("despite" in my opinion).
I had a lot of fun with Inquisition, but the MMOish world design and the fact that so much core plot was hived off into Trespasser makes it hard to call the game truly excellent.
Provided you use mods and community patches, sure. I had to replay all of Nar Shaddaa, and kept getting the bug where it's skipping all the dialogue. (Also, I felt my ending was underwhelming.)
Oh wait. They only made the first two. (The answer to your question is ME1)