In addition to what Juan and HW have said, I'd have to add the following...
a) The sheer scope of the conflict. You begin with an 'irregular' army with improvised vehicles against a 'regular' one little different to those that were around at the end of the Great War. At the end you have two 'regular' forces that are semi-mechanised, both uniformed and equipped, yet in the main still very different.
b) There's no overpowering weaponry on either side. The tank doesn't dominate and is still vulnerable when misused. When the most advanced tank used is the BT-7 and the most common (on both sides) is the T-26, how bad can facing an opponent's 'tank company' be?
c) 1930s aircraft and vehicles are so much more interesting, you have biplanes and early monoplanes and some seemingly 'Buck Rogers' inspired vehicles into the bargain.
d) WW2 as a 'historical' period has been done to death in books, with a lot of stuff simply being regurgitated in the 'latest new book'. The SCW is far less well-covered and each new work tends to bring some surprising revelations, which have been 'overlooked' in the official or marxist biased histories previously trotted out for it.
As has been said, it's an infantry heavy era, so it's ideal for 'platoon skirmish' games like Bolt Action or Chain of Command, or even 'company level' sets like Flames of War (no 'wall to wall' tank park like games here) or IABSM.
Your scenario options are also much wider. Depending on 'where' and 'when' you have anything from desperate street fights, trench-line assaults, patrol encounters, even the occasional armour on armour slugfest... the only thing it hasn't got is 'jungle warfare'.
If you are more inclined towards 'adventure' style games, you've got partisans in the hills (watch or read for 'Whom the Bell Tolls'), spying, counter-espionage and 'commando' missions (read some of Hemingway's stuff) and gun-running ('Rick' in Casablanca had an interesting career which prevented him from returning to the States).
There are some good ranges out there too. Obviously the Empress ones are top for my money, but the FoA ones come a respectable second, along with the odds and sods Northstar produce.
In 18mm there's an attractive new range from 'Warmodelling Miniatures' and in 15mm (18mm?) the Peter Pig range is being expanded and in some cases re-done. There are even some cracking figures in 10/12mm.
Minairons are working on a 20mm range, which having seen other work produced by the guy chosen to sculpt them, could be something else... certainly an improvement on the venerable 'Hotspur' range, which sadly doesn't cut it in today's world of super-detailed figures.
You might ask 'Why don't you play SCW?' for my money.
