Bioware and Bethesda are pretty much tied in my book. Bioware games have better stories and writing, and Bethesda games have better immersion.
But I'll say Bioware because the gameplay of their games is generally more enjoyable on a minute-to-minute basis. And the storylines have more emotional impact.
I absolutely love Bethesda too, though. And I like Square in general, but they're really not what they used to be. Final Fantasy XIII and XIV sucked. Unless you count Deus Ex 3 as a Square Enix game (and I don't), they're not even in the race anymore.
But I'll say Bioware because the gameplay of their games is generally more enjoyable on a minute-to-minute basis. And the storylines have more emotional impact.
I absolutely love Bethesda too, though. And I like Square in general, but they're really not what they used to be. Final Fantasy XIII and XIV sucked. Unless you count Deus Ex 3 as a Square Enix game (and I don't), they're not even in the race anymore.