Portal 2: More stuff to work with and is funnier.
Portal has a better storyline, but it's got to be portal 2 due partly to the greater variety of test elements and mostly cave johnson.
Portal has the nostalgia value, and the charm of being that one odd little game out of the big package that isn't like the others, but stands out on its own as having the potential to be something great. Portal 2 puts that potential to use by having more and better of everything: more complex story, far longer campaign (and two separate ones at that), many more testing elements, an overall smoother puzzle setup IMO, and something about the atmosphere is just more attractive overall. Portal 1 ranks high on my list of all-time favorites; Portal 2 takes what Portal did and makes it even better. So it wins for me.
Give me EP3 already, but Portal 2 was way better than the first one. I was sceptical about that before it released. Was also quite surprised about the availability of good maps when I started looking for more Portal 2 after finishing the game!
I like portal 2 because of the story, new testing elements,
Portal was a great mod, but portal 2 was a great game out of the package.
And portal has so many glitches, you can win in 30 minutes.
AND YES GIVE ME EPISODE 3 ALREADY!!!!!'
Portal really didn't have much of a story though. Portal 2 was much longer, had great visuals, puzzles, and test mechanics, was funny, and had a great story.