Indeed. Mass Effect 2 felt like a new game, despite the similarities of the engine. The graphics were improved, the gameplay was improved, the narrative was much better delivered, etc. I haven't played ME3 as it wasn't released on Steam, but it looks like an improvement again. It was the same with STALKER: Clear Sky, which (despite its faults) introduced improved graphics, new gameplay mechanics and a more focused narrative - unfortunately CoP took a backwards step with graphics, with a massive gameworld that didn't really have any personality.

No, it boils down to enjoyability. I liked TW2 for the narrative and for the environments, which had a very distinctive feel, much more than the combat. It's the same with Oblivion and Skyrim - they have very compelling gameworlds and strong writing, even if the RPG elements were very light. I'm sure they would have been even better if you could meaningfully influence the gameworld but they were compelling games that I enjoyed playing. NV just didn't have that. The engine was clunky, the gameplay tedious (after having completed F3), the game world wasn't interesting (to me it wasn't as compelling as F3) and I just didn't enjoy it - the entire game was hugely dated in comparison to what the rest of the industry was doing.