Oh, me too - and if I'd remembered her at the time, I'd have added Scorpina to the list (I'll slot her in now) - but just in terms of the most awesome they've had? Lord Zedd was just pure evil awesome, and I mean, you have to include Ivan Ooze - he was beating the Megazord until the comet came along. Dark Spectre commanded all the series' past villains (Zedd included), and the other two are awesome examples of conflicted villains (plus, Astronema's pretty and Zen-Aku's a werewolf).
Short of including the Evil Green Ranger, that list is as good as it gets.