Since the OTL 20th Century was obviously the worst that could happen, what could be the best-case scenario for the Russians, with Russowank excluded? The Tsarist Empire was bound to fall once *WWI begins, and to delay it only buys time for Nicholas II.
I don't quite follow: with increased Russian industrialization, and increasing problems for the German military in getting bigger funding out of an increasingly fractious parliament, Russian chances of surviving a *WWI get better with time. One of the reasons many in the German military were happy to see WWI break out when it did was that they felt their chances of winning a war would be rather worse in a few years time.
(admittedly, as long as Czar "pointyhead" Nicholas is on the throne, a transition to democratic rule that _doesn't_ involve violent revolution is iffy.)
One scenario I can see that would be better would be if the Russo-Japanese War can be removed. Perhaps Japan and Russia negotiate, or alternately the Japanese take a bigger bite out of China.
OTOH, the Russo-Japanese war help highlight some serious problems in the Russian military. Perhaps sans the R-J war the Russians are _less_ prepared than OTL when *WWI breaks out and get PWNd harder?
Whether or not the Bolsheviks end up in power is up to you. If the POD is early enough, by Nicholas II's time, Russia is a very different place indeed.
Best-case? A war or economic crisis serious enough to topple the Czarist regime, but not messy enough to give the real kooks take over. Given some smart politiking, it should be possible to hold onto the Ukraine and the Belorussians in some sort of federative union - heck, possibly the Armenians and the Georgians if there's a large and scary enough Turkish state next door.
Holding onto Poland will probably require force and not be compatible with democracy - holding onto Azerbaijan and Central Asia by force is actually less of a problem in that ruling over Swarthy Peoples without their permission is considered okeedokee for a democracy at least until the 1950's in a no-WWII TL, but is probably not feasible in the long run due to the rather substantial cultural differences. (The Balts and Finland I'm not sure of: perhaps some sort of autonomous arrangement is possible, the Finns OTL being fairly happy at first to work with the Provisional Government, IIRC).
Given capitalism, Russian economies of scale and certain advantages in being a "late starter" in industrial development - the few big Russian industrial concerns before WWI were probably quicker off the mark to develop US-type mass production techniques than the Germans or the British, which had a pre-existent "craftsman" tradition - Russian economic development has fair prospects over the 20th century.
The biggest problem will be the peasant economy, which may remain mired in Latin American backwardness for a long time without major reforms, and the impoverished peasant masses may well be a source of radical political movements of either the left or the right - or they may be denied a political voice by urban-centered political parties fearful of exactly such radicalism. Things will be further complicated as industrialization grows the cities, which will then suck in people from the overpopulated countryside. Russia was pretty rural at the start of the 20th century, but I suspect it won't remain so (alt-Moscow as Mexico City?). Sans the revolution, Stalin, and WWII, there will be a lot more Russians by the 1950's, although economic development will probably bring down population growth rates to the extent that the Russian population by 2008 will be US-large rather than India-large.
Russia in 2008: cold Mexico with 3 times the population and nuclear weapons, or a near-equal to the US with at least lower-end western European living standards? I'm not sure, myself - there seem to be so many ways for a country to scew up it's economy. My gut feeling is that in spite of it's worse-than-Latin-American backwardness in 1914 (yes, poorer per capita than Mexico - by a fair margin), a more-or-less democratic Russia has some advantages in it's prospects for modernization - vastly greater resource base, massive economies of scale, a formidable if relatively small intellectual elite, close economic association and easy cultural exchange (at least at elite levels) with Europe: but I'm not sure which of these is the _likelier_ outcome, even if we assume a successful transition from the Czarist regime to something which is at least lawful and representative of a fair slice of the population.
Bruce