Most fun races to play:
6. Goblins - Goblins train too slowly for their cost and statistical weakness. Poison is only useful with the archers. Cavalry is really hard to get early, and other useful unit types like pikemen are super expensive. It would work better if there were quickly-spawning goblin units of each type, and then trolls and spider riders were used as late-game units who cost even more but were even stronger. Only way to win is by rushing Shelob.
5. Isengard - Units are more expensive than the Dwarves but weaker, and mines were a cool idea that never came into fruition because it's so hard to use them. They have cooler heroes than the Goblins, like Lurtz and Saruman, so that pushes them higher on the list.
4. Elves - Just as Isengard, the units are too expensive. However, summoning Eagles and using such a wide variety of heroes is fun. They have cool spells, and those Silverthorn Arrows are so awesome when you get a full battalion of archers. I just wish that their melee units were better.
3. Gondor - Gandalf.
2. Dwarves - All of their heroes are great, even if Gloin refuses to use his first skill on multiple units, and their troops themselves are awesome. Guardians can counter archers by charging, who were built to counter melee units in the first place, and while they lack cavalry, the Battlewagons more than make up for it. I love that you can add a pair of units or some equipment to the back of it, and while they could have gone much farther with the idea, I think they're powerful enough with 1 upgrade. Too bad Men of Dale are so much better than axethrowers.
1. Mordor - I know Mordor isn't better than the Dwarves in terms of power, but I absolutely adore their heroes. The fact that you can have multiple of the same hero, while hard to manage, was really cool to me, and the single heroes like Mouth of Sauron and Witch-King are so fun. ESPECIALLY the Witch-King. He has to be the most OP purchasable hero in the game, even more than Gandalf. Plus, getting an army of attack trolls and charging right through the enemy's defences is so awesome with the Mordor music playing, and that moment when you finally get the Balrog as a power... The atmosphere of Mordor and diversity of units makes it my favourite.
What about you? I'm sure that the different versions will surely give us both valid reasons for liking a faction over the other.