A dystopian future in Japan, set sometime around 2030. It's a masterpiece in almost all of its forms, check out Stand Alone Complex.
That being said, I'm not sure what is my most favorite anime. I'll just look at the favorites in my list and type them out.
Mobile Suit Zeta Gundam - By a long shot my most favorite Gundam series, period. It's also nicely gritty.
Ghost in the Shell: Stand Alone Complex and SAC 2nd GIG - Both amazing series with thick content and plot, followed by amazing art and looks for the date of release.
Mobile Suit Gundam 00 Second Season - Both seasons are an edgefest, but they never slow down on the visceral glory. You might see some similarities to Zeta Gundam.
Gundam Build Fighters - Probably the stupidest, yet best idea for a Gundam series ever. It's real fun, and just like 00, the visceral glory is astounding. You might want to know something about the whole franchise before the characters start spilling their spaghetti.
Another - refer to my profile picture, it's a picture of Misaki Mei from the series. Can't really say it's a masterpiece or anything, but it's a nice time killer.
Turn A Gundam - Sadly overlooked a lot. Total masterpiece story-wise, impressive character building and world building. Pretty slow, but it speeds up in the last ten episodes.
Psycho-Pass - Refer to SAC. Similar setting but nicely done and with the sprinkles of modern CGI. Stay away from the sequel though. It's not really worth it.
I have a lot of "obsessions" that seem to fade off and on. Currently these would include My Hero Academia, Noragami, Durarara, Cells at Work, and Blue Exorcist (though I prefer the manga for the latter one). But Natsume Yuujinchou and Mushishi are series I've loved for years and that love hasn't really faded.