I wouldn't call Divine Divinity a Diablo clone.
But it starts as a diablo clone, and ends as a diablo clone. Combat and loot system are very diablo inspired, and also map with fog of war, but you can have multiple saves and you can quicksave. But it is also an ultima clone, it has lot's of interactivity (books, chairs, beds, random items), though you can't actually craft things except some alchemy formulas.
Quests are varied... I don't remember to many fetch quests, but there are a lot of investigative ones, and they this is where it diferetiates from a diablo clone: a lot of these quests don't have a combat focus. Writing is on the same level of larian games, funny and functional. World is huge, game is long, and there's a lot of variety of backgrounds, and they sure are beatiful. The end really is the weakest part, but by the time you reached it (if you manage), you probably finish it: It's just a big dungeon, and probably it becomes a diablo clone again.
Beyond Divinity is inferior, and I continued a playthrough from Act II, where I stoped playing, after the hype of D:OS, and I actually had some fun with it. It feels very brownish which was off putting in the beginning, but I managed to enjoy it eventually. The worst thing is the battlefields, a side world you can/have to enter that has a camp with NPCs that gives you random quests, and you must raid dungeons in successive levels. It's not required to complete, but it's a place to level up characters, it ends up being quite necessary. Being an OCD player, I hated and liked the battlefields part. has very little connection with DivDiv, since you're not in rivellon. But I loved playing through act 3. And the banter between the main character and his deathknight companion. The skill system is broken though, with some useless skills, like lockpicking, that is not really implemeted and you waste your points in it.
Div 2 I played first map to completion till you get the "dragon form". Same level of writing (fun), but the engine is the terrible part. The fact that the game doesn't feel like a divinity game is it's worst sin for me: while the first two games have elves, dwarves, imps, lizards, the second one has only humans in the world and it's hardly mentioned what happened with everyone else. I'll eventually continue my playthrough, after finishing DOS and BD. I heard that the expansion is a lot better, but I haven't reached it yet.
Music is great in all of the games, after all it's kiril. And even these games have all these flaws, you can detect the love sven and co. put in his games. I bet that they wanted Div Div to have the same level of polish D:OS have, and the freedom to make that game. And they are bro enough to go back and update these old games to run on new coputers with widescreen monitor support and such. And with beyond divinity, feeling a lot like a spinoff game, you can see they wanted to have a two disagreeing party members system, that are one of the main features of DOS. I believe they intended to do the two player system in BD in the way they finally did in DOS. DD and BD are games that would be perfect if larian had the liberties the had in DOS.
Oh, the graphic whoreism: DD is incrdibly beatiful. Great 2D graphics, very colorful, great world design, variety. BD is the same engine and graphics, only the charaters are now 3D models ugly as hell. The deathknight looks like it's wearing bell botton pants. They should stick with 2d sprites.