One thing worth keeping in mind is the fact that the first game was a small experimental project made as part of the Orange Box rather than a full-fledged title. It’s short and a bit simple but it was more of a neat bonus in a pack of other games, not a star of the show. That’s not to say your opinion is invalid, on the contrary, it’s just… between years of hype and the scope of the project, having Portal blow you away would be more surprising than your current feelings towards it, in my opinion.

As BurnWits said, Portal 2 is more of a full-fledged title in comparison. If you enjoyed the first game, there’s a high chance you’ll like the sequel. Will it be closer to the mind blowing expectations you had for the first one? I don’t know. It is however a bigger and more polished product so it might satisfy you more in that regard.

I do understand the unwillingness to increase your backlog though, I know this feeling really well too.