Liches aren't always Evil. In D&D terms, Elves had liches called "Baelnorns" who were mostly Neutral or Good, and who became undead in order to guide their family/society and to preserve lore. There were also good liches called "Archliches" who became undead in order to combat a great evil that would simply outlive them. Like in BG2, the Liches that guarded the Golden Body Parts of Kangaxx, they became undead in order to ensure that the horrific evil Kangaxx would never be unleashed on the world again. An eternal watch/vigil, so to speak.
Liches don't always appear to be rotting husks. Many can cloak their undead appearance and appear alive with illusion, while others can inhabit younger, less rotted bodies. For example, Szass Tam, one of the most powerful Liches and Mages in the Forgotten Realms, is several centuries old, yet he still appears to be alive, the only tell-tale sign that he is a Lich is that his fingers are withered, and every now and then the musty scent of decay wafts from him.
Don't forget how Bidderdoo Harpell nommed the neck of a Dark Elf Weapon's Master after he ran out of spells!
Lol, yeah, that was hilarious. A 6.5 - 7 foot Dark Elf (They practically never reach that height, usually 4-5 feet) Weaponsmaster got effortlessly killed by a Mage transformed into a Werewolf.