Now that I'm a little less busy I want to expand on my answer of why I like Dominions in a SP capacity even though it's really a MP game.
I like playing crunchy, mechanical RPG games slow. Really slow. I like playing defensively. I like feeling out all my options. I hate losing when I don't have to.
In this regard, Dominions is great. There's SO much to see. Dozens and dozens of spells I've never even tried to cast, split up amongst all the different factions, elements and spell schools. Tons and tons of unique magic sites offering unique stuff. More magic items than you'll ever get a chance to make. Tons of different units scattered over the whole game. So much you will likely never see it all in one playthrough.
So I like making big maps, having lots of AI opponents. The beginning of a game of Dominions is the usually the most fun part. You're new and you have to expand the boundaries of your empire. You start drawing imaginary boundaries based on the terrain, figuring out where you're going to make choke points. Thematically I enjoy imagining my empire growing, rolling across the countryside enveloping all these small, independent towns and villages, occasionally finding a sizeable one, before you eventually run in to a legit nation with a Pretender. Your army isn't large or OP yet and you don't have master spellcasters and all the magic researched, so resources and logistics matter starting out and victory is not always certain. I like naming my leaders, watching them become heroic, tracking their exploits. I like building my Magic Site finding crew, making sure I'm getting the most bang out of my lands that I can. I like making and equipping magic items despite the fact most of the guys they will go to will just sit in the back ranks anyways. I like taking my time, preserving my guys, winning and seeing what's out there.
Truth is though, I've never finished a game of Dominions. The game played SP against dumb AI reaches a point where you have too much to care about that doesn't actually matter. You've got more magic sites generating gems than you'll ever use. New territory no longer thrills or really matters when you control half the known world. All the fancy global enchantments just give additional edge you don't even need. You're creating commanders not for fun or effect really, but just because you need more bodies to cover the vast amount of terrain you now control, so they're no longer really special. The AI can easily be cut off, isolated and pummeled into submission so there's no real challenge for your masses of troops. The last 1/3rd of the game ends up feeling like post V-Day in WW2: there's a shit load of necessary clean up to do even though you've already won.
And when you bump up the AI to higher difficulties, what you still end up with eventually is massive stacks of dudes defending forts that you have to take apart one at a time, and the AI starts using spells to, if not beat you, at least annoy you by cursing your guys, giving them Horror marks, etc...
So basically I don't play MP because I don't want to be rushed, and I still feel more inclined to do less than effective things just for the sake of novelty, experimentation or flavor, rather than what "works." Because if I just wanted to win I'd play on smaller maps and skip all the flavor and nancing about on things that won't help me win directly....but where's the fun in that? Playing against people would provide a real challenge but I guess I don't play Dom to be challenged. I play it to get immersed, flip on some classic, bombastic RPG music and just enjoy playing God, subjugating a fantasy world.
That's why I think Dom is special. It's a deep strategy game that can be appreciated multiple ways by multiple kinds of gamers. Doesn't mean it's going to please every gamer at all, though, and I don't blame anyone for finding it dull or slow. At the end of the day Dominions to me is like Risk with multiple sublayers of mechanics...but still essentially Risk. I don't really enjoy Risk, but I enjoy Dom because there's so much more to it than just capturing territory. Maybe one day I'll have exhausted all the novelty and know enough about the game to want to try my hand at some real strats against real people. But for now it's absolutely not necessary for me to continue to love the game.