Unfortunately you really can't compare one ability to another. Entire kits have a big impact on the game. For example, Amumu vs Maokai. Maokai has the easier time ganking with his targeted gap closer vs Amumu's skill shot but amumu can be very much more game breaking for the enemy team.
That said I've always found it strange how melee champs usally just have to string together auto attacks to get effects. characters like Jax, Xin, Vi, Vayne, Varus off the top of my head get bonuses just for attacking the same target multiple times.
mean while most (if not all) AP casters have to string together skill shots with targeted abilities in order to get effects. I mean it just seems much more of a punishment if you miss a skill shot with a caster then if someone gets away for a sec to reset the auto attacks.