Culture, Space and Diplo are all viable in CiV. However, you're indeed pretty much bound to get attacked at some point, but you don't have to take enemy cities - just kill the invaders.
All 3 of these work very differently from IV, though - in ways that don't favor a builder play-style.
For Culture, you limit yourself to 3-5 cities so as not to increase policy costs (which go up with each additional city you control), then limit yourself to unlocking a set amount of policy trees, then build a "Utopia Project." Seeing as policy trees unlock based on the era you are in, you'll pretty much always take every single policy in the first 3 unlocked policy trees. It's an incredibly narrow and stifling victory type that allows for little to no variation and locks you in to a set play-style throughout the whole game. If you choose to go for a culture victory, but have already built 10 cities, well that's just not going to happen.
Diplo victories consist of you saving up your money until yourself or someone else builds the UN, then spending all your money to buy up all of the city states for their votes. It's a pay to win mechanic, and it's viable for pretty much all play-styles, but it's also incredibly shallow - and the AI is therefore most efficient at it compared to any other victory type due to their gold bonuses.
Space victories are similar, except you have to manually move your spaceship parts to your capital once they're built. Needless to say, with the state of the current tactical AI, AI opponents never really get this victory type if you're paying any attention at all to what's going on on the world map.
By the time any of these are viable options, you might as well have just taken out all of the AI capitals for a domination victory...
Victory types are one of the areas I would hope get some attention once the .dll is released, (along with the points system, as right now there's no incentive for getting early wins, as this isn't really reflected in your final score).