I just beat Civ V on Immortal with India through a science victory with just two cities. Fuck yeah.
Thankfully all of the bloodthirsty assholes that surrounded me the entire game were very keen on murdering each other all the while putting on a farce declaring friendship to me and entering research agreements to gain my trust and to get me to lower my guard. I never opened my borders to anyone except Darius because Persia was science focused like me, busy fending off Siam and Mongolia and they just happened to be a fair distance away from me. Whenever other civs started circling my borders I just ramped up production of indirect fire and naval units. If anyone tried to take a bite out of India, I would've been pretty unappetizing. They would've lost a lot of their army in the open seas and more on my tiny island before they took either Dehli or Mumbai. Towards the end the Siamese, the Romans or the Danes probably could've wiped me out if they tried hard enough. Their armies were easily ten times larger than my own but they were busy murdering each other.
It was kind of tense near the end, waiting for research agreements to come through or for great scientists to spawn to help leap frog me through the technology trees. Especially when the other Civs were making greater progress with their own space programs. I had the Apollo Program and the ability to make the SS cockpit but was three tech branches behind on being able to make robotics/SS Boosters and open up the two later branches, particle physics/SS Engine and nanotechnology/SS Stasis Chamber. Each branch I researched I saw another Civ making that component of the spaceship. It's just that none of them happened to make all of the parts. Caesar was one SS Booster away from beating me while I waited the last five turns for my Stasis Chamber to be produced. It was so painful clicking the Next Turn button near the end, I kept expecting to lose, especially on that final turn.
I think I'll use India for the Deity run. Having a consistently happy populace with just one or two cities makes such a huge difference. It's bad enough trying to deal with the other Civ's advantages in the higher difficulty levels, when you compound the problem with an unhappy populace that slows your growth, lessens your productivity and decreases your armies ability to fight/repel enemies, it's almost impossible. Instead of climbing just the tech trees, creating the buildings and Wonders you need, you're diverting productivity away to unlock more superfluous things or getting beaten to your goals. With India this is less of a problem.
I love this game.