Thanks for the contributions, most of you.
I can't say I'm equally indifferent towards the three time periods, though I'd be moderately comfortable with roleplaying in any setting, really, just as long as the conditions align with my preferences.
Past roleplays I categorize as either classic fantasy or historical. The latter, I've found, are fun in-concept but difficult to write for in the long run. It requires a lot of prior knowledge and/or willingness to research.
Present roleplays—and I'll agree with STARDUST here—are the most enjoyable with fantastical elements added on, but, overall, I prefer my roleplays to be grounded.
Futuristic roleplays tend to involve a lot of technobabble and complicated mechanics, I've concluded, based on past observations on different sites. Personally, I love future settings, but when the mechanics start reflecting the complexity of all the technological advancement and the like, I immediately lose interest. No to mention there's so much lore and explanation of how the world got this way that I can take before I begin to feel isolated. How can I contribute to a world that's already been described in fluent detail by the game master?