I've been playing Heroes of Might and Magic V, and I just love how this game has been polished.
I am now doing the necromancer campaign, and I have always loved this race/faction.
Necropolis units are unaffected by morale, so the only thing is to ensure luck is up all the time.
The Liches and Archliches are my favourite units, aside from Skeleton Archer. The thing with Skeleton Archers is that you can amass thousands of these things. 3,000 Skeleton Archers vs 25 Titans. I'd go for the Skeletons.
If you have one of those artifacts that ignores range penalty, that's it. There's no army that can withstand my ranged undead units.
Except for Inferno troops with their gating abilities. And some forms of magic combo.
The easily-managed undead troops are also quite a boost. Undead is basically still my favourite thing in Heroes.