Well, of my rankings, bear in mind they're not all that stable. I tend to switch who my favorite is based on whom I had the most fun with. Currently, it probably stands as
2) Personally, I love the German endgame. But maybe it's the sort of player I'm in. I love those last stands against overwhelming odds, fighting for each inch and each second. Yeah, you can't counterattack; that would be breaking the spell. It's all about retracting your line, budging just enough to not collapse, but giving up each hex only after you've made them fight tooth and nail for it. Glorious.
3)I play a lot of solitaire, and it might be affected by the optional rules I tend to like, (But hey, solitaire insures two evenly matched players, right?) but I find the Soviets "Survive" against a blitz 41 about 60-75% of the time. That being said, I get a lot of games where the Soviets are lamed, and never really muster up the sort of strength to do the counterattacks like they historically did.
4) I've tried a few "China isn't a big deal" games, but even then, I'd go for those two resources in the south, Si-An, and Chang-Sha to solidify my line. Completely ignoring the Chinese is very dangerous, they can build up faster than they look.
And if you're NOT going after China, you should probably be going after the Soviets, hard and early, and then when they force a peace down your throat, being ready to support your German buddy in 1941.
But just sitting there passively is a losing game for the Japanese. At the start you have a grand total of 10 resources under your control, and another 6 coming in from the NEI and the U.S. Once you subtract the amount you're spending for oil, you don't really have all that much production, and even the amount you'd save by not letting the U.S. in say, two turns later is enough to justify that. They'll come in two turns later, and ismply smother you.