In my opinion (and it's an opinion), I think a game has to meet one of a few qualifications to be considered a console port:
- The game engine would have to be designed and tweaked in such a way that it is optimized for a performance threshold which falls in line with the performance capabilities of the next gen consoles. Meaning, the game engine will not run as efficiently when higher settings are used, even on high end PCs. (An example of this is GTA IV on the PC. There are countless complaints of people who have extremely high end systems who, when using max settings, get between 30 and 40 FPS.)
- The game engine has few graphics options. This is usually due to the fact that the game, being developed for the predefined hardware found in consoles, was not directly designed to be scalable across an entire range of PCs. (An example of this could be Crysis 2. The game engine, being developed using DX9 and optimized for consoles, uses a simplified graphics control that restricts the user to a few predefined quality levels, so as to make sure that accessibility is maximized and that the game itself functions correctly and efficiently.)
- The game controls feel clumsy and awkward on the PC, yet natural and comfortable on consoles. This is usually due to an extensive amount of testing on consoles and a lack of testing on PCs.
- The game assets, such as textures and models, look best using television resolutions, but begin showing flaws at resolutions higher than those.
Now, these are really things that make me think a game is a console port. If someone feels any of those things about Portal 2, then they're probably right in saying that, to them, it feels like a console port. However, I wouldn't consider an art asset like the menu warning a valid point that the game is a console port. I think that the actual game, visual or gameplay wise, has to show signs like those listed previously for me to consider it a console port. (That's just my opinion of course, which is worth roughly 2 cents.)