World of Warcraft Analysis - Critical Strike

Critical strikes are hits that deal much more damage than an usual hit and triggers abilities/talents that look after when critical strike occures.

A melee critical strike does 2 times of normal damage, where as

A spell critical strike does 1.5 times of normal damage.

The reason spell does less is because spells are ranged, and it is kinda imbalanced if two critical spell strikes hit on the same target.