HL2 is a bad example because it created similar reactions and would have also benefited from a more conclusive ending? You may need to explain that one.
And the fact that there was an 'outcry' was essentially my point. In spite of that, and after perspective kicked in, HL2 was and still is widely considered an outstanding game. HL3 is still one of the most desired titles in the industry. HL1 is still beloved. Sounds like a far cry from a "whole series ruined" to me over one inadequate ending.
Again, kind of mirroring my point but saying a different thing, if you've 'invested' a hundred hours into a game and the last few minutes aren't up to snuff, why does it negate everything else? It's a minute fraction of your time, emotion, and interest spent. Is each individual minute of the ending you watch really more important than 20 hours of what you play and do? I get that you want a more complete ending, I just don't see the rationale behind "This part is so much more important than all the other parts put together."
Another example that struck me was Shadow of the Colossus. Weird, sort of fits sort of comes out of nowhere ending with little resolution and kind of ends abruptly iirc. I don't even remember it that clearly aside from the riders and your transformation frankly; on the other hand I can still vividly picture almost every individual Colossus in my head and how you beat them as well as riding through the vast open wilds. Not as story centric, true, but still an outstanding game with a lackluster ending. But that's not what people remember; it certainly didn't make or break the game.