ZeroMachine said:
I'm deciding between an eternal love interest, or an eternal friend...
... I'll go with friend for this case, because I honestly can't think of any character I could fall in love with.
I'd probably go with this same thing, but pick Chris Redfield, because if I am going to have a companion for the rest of my very long life, I want him/her to be relatively mature (which rules out most DA2 options), good-natured (which rules out most JRPGs), battle-ready (which rules out a lot of NPCs), have an 'other people' oriented moral compass (which means the mature, battle ready, good-natured people are probably ruled out by now) and to be a soldier (for the 'get the job done', 'don't need golden palaces to survive' mentality). Not many characters seem to fit this bill, so while Chris isn't exactly the most exciting companion, he is very much an 'in for the long' type person.
Also, I would love to learn how to fight, so an elite soldier seems like a good teacher.
EDIT: A spiderman symbiote wouldn't be that bad either, as long as it didn't try and take over my mind. I mean, enhanced physical abilities, some measure of companionship, the tendril-web-things, and the fact that it can shapeshift into clothing (which also means I don't need to carry around a spare super-hero costume) means it is highly practical, would augment my already near-unkillable-ness, and allow me to swoop in all hero-like without giving away my identity.
Also, if this companion is meant to be for my entire life, ther isn't the risk that it wil run off for a better host.