There is so much to talk about at the moment it is difficult to know which way to go. BBB wrote an excellent post on Garrisons which negates anybody else writing about it until we have more detail. Rohan at Blessing of Kings, discussed the Orc Centric expansion, which is the point were I put in my two-penneth.
Having never played Horde, and preferring the pretty races (Blood Elves don't count), I have a slightly skewed view of how the factions are treated. Trying to be neutral in my observation it would appear that the vast majority of players are Alliance based. This is only natural because that is what the Fantasy genre as always taught us. We see everything through the "good guys" eyes. The first books in the genre are attributed to JRR Tolkien (Hobbit and Lord of the Rings) set the tone for all future books. The "good guys" are Dwarves, Elves and Hobbits, with humans being weak and fallible and both mighty and strong. Orcs, Worgs, Trolls and Ogres are the "bad guys", and so Blizzard had a uphill struggle to balance the factions.
The original Warcraft franchise like every other Real-Time Strategy game, involved a storytelling through all factions. In the series I remember very little except for 4 storylines.
- The Battle of Mount Hyjal
- Grom Hellscream drinking the blood of Mannoroth
- The Horde helping Cairne Bloodhoof (or the other way round)
- Arthas culling Stratholme
Vanilla WoW was heavy in favour of the Alliance due to the aspects that I have mentioned above. The Horde would later flourish when the stereotype of the Alliance as being casual, carebears and kids. The Horde on the other hand was for real Raiders, PvPers and Hardcore. Horde numbers swelled but on the whole the Alliance still holds the larger numbers on most realms.
Blizzard picked up the baton for the underdogs and have on the whole had a slight favouritism towards the Horde (which is perfectly understandable). Not wanting to pick out too many individual acts of favouritism it is easier to look at the expansions.
- Vanilla - The Alliance had the lion share of non contested zones
- The Burning Crusade - Probably the most Neutral in terms of Storyline
- The Wrath of the Lich King - Alliance centric due to Arthas being the fallen Alliance noble
- Cataclysm - The hero in a supposed neutral role was Thrall, and with the Horde making territorial gains in the revamp.
- Mists of Pandaria - Garrosh Hellscream (enough said)
- Warlords of Draenor - Garrosh, Grom et al. This is completely Horde centric.