The battlefield view in H4 pretty much killed all enjoyment of the game. It's both fugly and hard to read and the units look like ass.
Though it did try to innovate (perhaps too much) and iirc had way better campaigns straight off the bat.
So, if you're a storyfag, you may look past its flaws.
Mechanically speaking, H5 was an attempt to make a H3+, curbing some of the cheese (magic, necromancy), not trying to reinvent the wheel entirely,
but trying to catch a middle ground between innovation and feeling right at home. So, theoretically, if you liked H3, this should feel right at home.
However, the game lost the smoothness. The 3D view is at least partially to blame for this.
Sadly, the style also seems to have caught the warcraft cancer.
I remember the original campaign was meh. It's worth giving it a go with community mods and expansions.
A bit of context is important to understand why these games were received the way they were.
After two really, really solid offerings in the series, H4 felt like a slap to the face for a lot of fans, because it simply felt like a knock-off.
I remember myself thinking: ok what the fuck is this shit?
So yeah, nobody had any hope for Nival, especially that NWC and 3DO were no more, but they really tried to bounce back on track with V.