Yeah, so the endings thread got me thinking.... I haven't even *seen* the ends to countless games I've played... but I've seen (more or less) every beginning to every game I've played... so here's my personal best & worst from recent games.
Best: Mass Effect 2 - I jumped into the demo not knowing what to expect and immediately ran and purchased ME1 after being blown away. (both figuratively and literally). It didn't hurt that it was a great game altogether, but the opening scene was like playing a AAA scifi movie tailored to your personal choices. (I GREATLY appreciated the little changes after continuing from ME1)
Worst: Fallout: New Vegas - I love the game, really I do, but it took way too long before I reached the titular 'New Vegas' and really started getting drawn into the game.