I reckon the lich sucks. I can never win against anyone with the lich.
I almost choked when I read that. Do you have any idea how powerful that hero is?
The Lich is one of the most potentially dangerous heroes in the game, but he requires a good deal of babysitting to really harness his power.
Ok, let's start off with skills.
Frost Nova:
I rate this as the best non-ultimate spell in the game. It's an awesome unit nuke, dishing out 50/100/150 damage to units surrounding the hapless target and slowing them as well, allowing your troops to have a field day, kinda. Not just that, but it's an awesome hero killer. At level 3, it deals 250 damage to the target, and slows them as well. Throw in a level 3 Coil and you're looking at a badly wounded hero.
Frost Armor:
The armor bonus is pretty nice, and the cold effect is great too. It's not quite as useful as Frost Nova, IMO, because AoE seems to be the way to go against UD more often than not. Plus, it's cheap in terms of mana.
Dark Ritual:
Yeah, it's kinda bad to sacrifice one of your own troops, but this is a really cost-effective mana regenerator. At level 3, you get more than twice the mana from sacrificing a healthy Ghoul than you would from downing a Mana Potion, for 10 gold less as well. You eventually won't need this though.
Death And Decay:
Ehh, it could be better. But it could be worse too. IMO, a game should be decided before Ultimates come to the table.
Now, about the Lich himself... He's a physically fragile hero, easily killed by just about anything, but he has a HUGE Intelligence stat. He has the highest Intelligence out of any hero and, sadly, has the highest DPS out of any Undead hero. Because of this high Intelligence, his mana regenerates very quickly as his level grows higher and higher, which is why you eventually won't need Dark Ritual except in the most dire of circumstances.
Being the fragile bag of bones he is, he probably shouldn't be used alone. But, IMO, NONE of the UD heroes should be used alone. They are all so much more powerful as a team. For example, when you use the DK and the Lich together, you have the ability to heal the Lich, but also the ability to nuke the enemy heroes. With DL/Lich, you can own masses of units by spamming Carrion and Nova.