Here is an answer.
Your main condition should be the screen. Witch Samsung galaxy S 2 has the best, also the gpu power is very good if not the best, go to gsmarena and check for review on Samsung galaxy s 2, optimus and htc sensation or something like that. See witch one does best.
Found the link:
http
/www.gsmarena.com/htc_sensation_vs_galaxy_sii_vs_optimus_2x-review-608.php
Here are the pluses for SGS 2:
-infinite black lvl
-very low power consumption for the screen, super amoled plus
-big screen
-low weight
-everything you need to have in a smart phone
-very smooth scrolling on web pages and very smooth movements wile changing screens because of the dual core 1.2Ghz CPU and touch wiz 4.0
-android 2.3
-16Gb internal memory
-1Gb of RAM
I have the original sgs i9000 and a friend has s2 and i can really see a difference in speed ans smoothness. And thrust me when i say that i know what i am saying.
I think that the optimus has a brighter screen but you can not see the difference only measure it. All of those you mentioned display different colors from different viewing angles. With super amoled plus , as with super amoled you see the same colors from any side and angle.
There is also an sgx 2 witch is on tegra chip set but it has lower net speed, smaller screen and some shortcomings. I wouldn't buy that. Probably when nvidia releases the next generation of tegra chips for smart phones and has some experience. Samsung already has experience with it's PowerVR SGX graphic processor.
Samsung make's their own stuff and also make's stuff for others.
Also Samsung galaxy x2 has super LCD not super amoled plus.
About the optimus 3d, i can say anything. You will have to check it in a store and see how it works. 3d is also new to mobile phones. You have a preview on gsmarena.com also on the optimus 3d.