Basically Heroes V = Heroes III + WoW and anime-like graphics (angels with giant swords, etc.) + poor story. Oh, and some units look like they were copied from Warhammer (dark elves, dwarves, orcs, etc.)
Nival just did copy + paste, added some features, like skill system upgrade (those perks like ballista triple shot) and called it a day.

I actually perhaps Age of Wonders: Shadow Magic. I find it deeper. But that may just be me.
Karl

Wow, I tried the Heroes V demo, and liked it. Here I am, preparing to buy the full game, thinking it is going to be as open-feel as Heroes 3. I guess I'll avoid this after all.

if you like the game buy it if not buy the gog games

My 2p's worth (HOMMV).
Campaign was dreadful.
So linear you could use it as a ruler.
Either I approached this game in the wrong fashion, or the designers decided that there is no room for any personal strategy other than following an exact preset path.
I just felt as though if I don't go immediately to point 'A' and defend castle with 'X' forces then I will lose.
There was no freedom (well none I could find) especially later on in the campaign where it just got too hard to enjoy.
HOMM 1&2 are the only ones to consider imho (I missed 3 & 4 so cannot comment).

There doesn't seem to be any point in hiring new heroes on most of the maps, especially since they all start at level 1 compared to your level 17 or whatever main hero. It seems like the point is just to rampage through the scenario with a single army, which is an idea that King's Bounty did ridiculously well but that doesn't fit Heroes V's gameplay mechanics at all. I got about halfway through the inferno campaign and then pretty much lost interest...

Another thing I dislike about HoMMV is that the hotseat is damn slow. I remember playing HoMM II with two friends on the same computer for hours... HoMMV was just too boring.

You don't want to play extra large maps in Heroes V unless you have a movie to watch or a book to read when you hit the "end turn" button. Because of this it is a pain in the arse to play larger maps.

Well, as far as I am concerned 2 and 3 are the best of the series. 1 was a bit too simple and 2 evolved into one hell of a gem, 3 was a very nice gem as well. Then came the dreadful 4, with a few good changes/additions and 10x as many bad ones. I never actually played HoMM 5, but I saw a friend playing it a lot and frankly I was somewhat put off by it. The graphics in the gameworld/combat felt wrong and as earlier mentioned...the corridors. That really put the game off for me.
The skill system seemed somewhat interesting though, but as I never actually played I can't say to 100% what I feel about it.

I think that HoMM 4 is a pretty good game. Is not a real HoMM, but killing an entire army with your barbarian hero never gets old.

Funny thing is, I noticed this on most any map once you got going with a few characters out, in HOMM2 especially. I first got it on one computer and the time between turns got aggravating. When years later I moved it to another that was twice as fast, for some reason the AI still took a long time to make it's move. I'd have to say this is the only thing about that franchise (I only played 1 and 2) that I disliked.

It's been a while since I played it, so I don't remember the detail/campaign, but I remember pwning someone I wasn't supposed to beat, and then the cutscene came on with the opposite result...
Honestly though, I didn't mind the gameplay that much, and the battles and gameplay graphics were survivable some of the time, corridors only a slight annoyance, but they gave the game some of it's own strategy/flavour...
What really pissed me off was that after expecting a really crappy game with some effort in the let's-make-shlit-3D department, I got an ok game with NO EFFORT, no effort at all, the campaign cutscenes were $#$%&%$#^@&#$64ing *DISGUSTING*, the story was horrible.
I don't care about graphics that much, but the presentation of the campaign was so horrible, and literally years behind any games I had played recently, I just couldn't bear it.

The 3D engine is what bugged me the most about Heroes 5.
I find it way too difficult to discern a ressource, chest, gold, artifact, mine w/e from scenery.
It also suffers the same problem that C&C Generals suffered from, the camera is like, 10 feet from the ground. Yeah I am exeggerating but I feel that my overview of the situation is extremely limited by the camera.
More games need supreme commanders innovative zoom and strategic overlays.

I played countless hours of EVERY HoMM game, both solo and with friends (LANs or hotseat) and I enjoyed actually every one of them.
Sure, HoMMV is different and the 3D needs some adaptation time at first when you are accustomed to the 2D HoMMs. But it is a very good game indeed. Yeah, it's true, it was very buggy at first and it's a shame Ubisoft released it in that state. But the patches and the two add-ons made it a really good game.
Not like King's Bounty, which i regret to have bought because it's one of the most boring games i've every played...