Personally, the list of brilliant endings are as follows, and I warn for spoilers:
Deus Ex (all of the endings):
It's been a long time since I've spun this disc in my PC, but I recently picked my intrest after becoming burned out on World of Warcraft. Whilst the graphics are dated compared to the current generation, the old Unreal Tournament engine holds up quite well for this outing. It lacks the atmosphere of System Shock 2, but the sheer scale of the tale is mind blowing.
Half Life 2: Ep 2 (Kick in the goolies, but awesome nonetheless)
Valve seem to keep outdoing themselves at times, and I personally wish that more developers would take a leaf out of their book, but on the other edge, glad that no-one does.
With such well defined characters, and ones that I've grown attached to, it really is a massive ball-buster to kill one of them off. It was the same feeling as watching the Futurama episode with Fry's Dog, Seymour. I became so wound up in the struggle, I was expecting someone to come in and save the day, as I expect a bit too much, being the jaded and cynical bastard I am; but I was genuinely suprised at the ending of Ep 2.
Max Payne 2:
This was mentioned before, but I'm in total agreement. Brilliant storytelling in a shorter package, but told in the true Film Noir style. I can't say much more about it, I enjoy it so much.
Day of the Tentacle:
This was one of the most goofy, oddball games I've played, one of the brilliant games from my childhood, and as humourous endings go, the boys from the LucasArts creativity department made some gems. DoTT's ending comes as an epilouge, after saving the world from the evil Purple Tentacle, there's the awesome scene of our three nerd-heroes all trapped in the same suit of clothing. I was crying at that ending the first time I saw it and it still makes me giggle each time, although not as much as some of Murray's lines from Curse of Monkey Island, or some of Sam and Max's lines fro Hit the Road.
Knytt:
Although later I will prattle on against simplicity, but I want to point this out now: Whilst a simple game claiming complex is pretentious and really annoying, simplicity for the sake of simplicity is a rare sight. (See Painkiller) Knytt is a freeware gem from Swedish developer Nifflas. Whilst the premise of the game is at heart an exploration platformer, there is such a little hint of story that just tied up the whole package.
In a nutshell, the titular hero of Knytt is abducted by a rather evil alien from her home planet, away from her family. Mid-flight however, the ship crashes, and both the black alien and Knytt are stranded. After a massive world and about 4 hours of gameplay, Knytt finds all the parts needed to fix the ship and the black alien takes Knytt back home as way of thank her.
There is one thing I want to point out: This is all done without words.
Deceptively simple, yet it was such a sweet ending, it's stayed with me.
Uplink:
Introversion Software's first game, and one of the closest examples of how to make a game without fancy graphics. The interface acts like another desktop, and after you break into a few computer systems, a plan is set in motion to destroy human society through the destruction of the internet.
Brilliantly executed with the player able to take either side and put things right or wrong, and there is no black/white, both sides have a moral highground and deciding which way to go is hard at best.
and for the last, I'm putting on an asbestos suit for this:
Freelancer:
Possibly one of my favourite space-based trading games, horribly unrealistic, yet utterly satisfying when either going through the Single Player storyline, or (through mods) playing in the open sandbox mode. The story plays like a classic space opera, not concerned with hard scientific facts, but more on characters and storytelling. I admit, it's cheesy, but part of me thinks the developers were aware of this and tried to improve the gameplay as much as they could to make up for the rather over-the-top acting at times.
Yet even with that, I genuinely grew attached to the characters, and to the universe in which it was set, and wanted to save it from invasion by a sentient race of jelly aliens.
Tacking the epilouge hinting at a sequel was pointless, however, but I guess you needed something to keep you exploring.
I also agree with a lot of the games listed before my post, but I just want to point out my disagreements with a couple of notable examples:
Bioshock:
I know it is one of the more higher class FPS games out, but I believe Yahtzee said it bes with "It isn't like System Shock 2, it *is* System Shock 2."
I've spent many untold hours playing SS2, and it's pretty much a slap in the goolies to have that gem unnoticed by most of the gaming press until enough money was given to hype Bioshock.
Admirable effort, but not that great.
Any of the Halo series:
I know I'm not really qualified to judge this, mainly because I never got past The Library on the first game and never touched the single player campaign of any other Halo since, but from everything I've heard from the many Halo fanboys I know, I can get the gist of the storyline, and it's nothing that special.
The Final Fantasy series:
There was a point in my life where I would agree whole-heartedly with comments about the greatness of Final Fantasy, but my love for the series after not touching them for two years and then picking up XII. A sudden light came on, the penny dropped that FF, whilst has some excellent character moments, are almost juvenille in their simplicity, yet trying to claim to be deep and thoughtful. To every rule, there are some exceptions, and Square made the best Final Fantasy at VIII, with some of the most jarring storytelling there. A shame that most other JRPGs couldn't move in that direction.
Just my two cents there.
--Ninja
A small postscript:
I understand I only have one post and you will think I'm a newbie or whatever, and how I should go post in the newbie forum and announce myself with some innane statement about "LOOK AT ME! I'M NEW!!!" instead of just getting past that and getting onto some serious, intelligent discussion. I apologise for not doing that way, and I just want to get into posting.
Secondly: Whilst I understand that grammar is important, and that people should take time in editing, not everyone was an english literature major, and not everyone has a grasp of the english language as others do. I honestly think that a one line remark, only four posts after the start of the thread is *not* the way to encourage people to use decent grammar, actions such as this only serve to incite flame wars.
There's another two cents. I now sit on $0.04.