It's all subjective and depends what is acceptable. Just like many here who state non-retina ready Office 2011 and CS6 look 'fine' with retina scaling (it looks horrible to me) 1080P IMHO is even worse than 1440x900 as you're not running a properly 2:1 scaled resolution. Are you playing Java games or what? Try running the game at full 2880x1800 vs 1080p, anything other than full res will look 'fuzzy' in comparison.
i'm running all sorts of games, WoW, BF3, crysis 2 etc, 1080p or 1920x1200 (to fill out the whole screen) looks just as good as my friends laptop with same specs.
i don't think theres any doubt that 2880x1800 looks better.. but thats not a resolution for a laptop gaming so thats kinda useless to discuss since it's not playable (60+ frames)
i have my real world comparisons, and for me a full HD laptop and the retina macbook pro at 1080p or 1200P is just as good.