Its not the say Stardock wouldn't do a great job with more realistic graphics, has they did it with Sins and DemiGod. What gives Elemental the cartoon graphics appearence, is the 2d feel (has if it was draw; the contours arround everything) and the colored graphics. But there is a painting feel to it that breaks it; the mountains, the ground/grass, the ocean waves and the bird here: https://www.elementalgame.com/Screenshots/Kingdom_Scott_City_1280.jpg
A game like King's bounty, is a game that want to have cute graphics(compare the first pic's castles with Elemental castle):
http://pcmedia.ign.com/pc/image/article/901/901391/kings-bounty-the-legend-20080820105241306_640w.jpg
http://fidgit.com/kings_bounty.jpg
http://gry.o2.pl/upload/files/Kings_Bounty_w_d_10.jpg
Look that there is no real scale for things in there, and how the castles are small and fat. What I mean is that Elemental graphics, aren't meant to be cutie. Scale for exemple is a important thing that I like, I like that the citzens and windows are very small comparably(this allows dimension to the castle, it feels like a huge structure has it should be realisticaly). Also comparing the colors present on Elementals pictures and in King's Bounty, the latter is much colorful. The colors in Elemental are even a bit darker, the ground in the dense part of the forest is dark brown, the downright part of the ocean is dark green has is the mountain's green, the roofs of the castle are dark red. Just try to compare it with another colors.
It feels suficiently dark to me comparing to other games. Not too much bright, not to much dark. It isn't to say, I don't like games with very brigther or darker coloring style. But without the shading is looks in the balance to me if I were to call it bright or dark in its colors. But the game uses many different vivid colors and biggest thing is that there isn't much color variation. Maybe with the shading, the trees should cast shadows on each other for exemple (but I don't understand much about it)
Indeed games that use contours and are colorful are usually called cartoon style. What I try to say is that it isn't bad and it isn't exaggeratedly so(nor is explicit cute). Games like Fire Emblem GBA, Zelda, many Final Fantasy's, even Kings Bounty are great games. In the Kings Bounty forum I used for exemple, many congratuled the graphics and the feel it gives.
I'll show a pic from another game that could probably be the realistic representation of Elemental's, notice even the pink trees. This game graphics are really amazing and artistic and follows another style. But Elemental's is also great style for me to look at.
Is it impossible to call these so realistic graphics cute? I think it is too, probably because it is a board game.
Elemental could be a great game in those graphics, has can be with the current. They are just different styles. I would never say a dark fantasy game would suck, it can be great, is just that a colorful style doesn't generaly suck and how it was used for Elemental isn't a exaggerated cute thing, since it is less cute than many games.
Not to meantion that graphics are close to nothing if the game isn't good. Also, graphics range till animation and other things. It's kown that the animation of the battles of Elemental are being designed to be great and fun to watch. The pic I showed is from ROTKXI, but that game have simplistic battles without animation and not many strategic options. Even Civilization isn't close to the realism of ROTK graphics, probably because those are more representative games with much bigger maps (ROTK is just ancient china). You usually have to represent a river or mountain small because of the range, while the rivers at ROTK are and can be huge, because the scope is not big. And lets consider Elemetal is fantasy theme while ROTK is more historical theme which doesn't mean one couldn't possible be portraited very well with the contrary designs. Fire Emblem was one of the greatest games I played, and the graphics were a small colorful GBA graphic, tough I played many PC games.
Tough ROTKXI is a good (~8.0) game, in terms of graphics you won't see battles like this there (or more than little animation):
This pic, IMO don't forces to think about cute, but beautiful instead and first. It looks colorfuly dark and magical and the designs are modeled to realistic scale (men to horses, men to catapults). It looks like cartoon because of a design choice.
To like styles is a matter of opinion, I'm giving my vision and why I like it. The only thing I would stand has a fact is that Elemental art do not make use of very cutish style, since it is a different thing. Still someone can find it very cute or not.
