After the genius ending in Portal, there are some second places:
-Zelda: A Link To The Past (SNES). It's kinda cool to see how many of the characters you met in the game are doing. Not many games take the time to do that.
-Ninja Gaiden (NES). Since the game has many cut-scenes it seems like the cut-scenes when put together are a ending video.
-Castlevania. I love watching the castle crumble, it gives you a sense of fullfilment. Extra kudos for the Super Castlevania IV (SNES) and Castlevania: Bloodlines (GEN) endings.
-What about Megaman 2 (NES)? Very cool Megaman walking while the seasons change.
-I really love the ending in Actraiser 2 (SNES), the statue of Master being afflicted by the weather and time, very cool.