1. Darth Sidious
2. Mitth'raw'nuruodo
3. Admiral Ackbar
4. Darth Revan / Darth Tyranus (Revan wittingly went up against the Sith Emperor and got his ass handed to him; Tyranus got captured by pirates)
5. Wilhuff Tarkin / Darth Vader
6. General Grievous (didn't just order his droid troops to shoot Obi-Wan for some reason)
Canon is pretty much the same, except Revan doesn't exist in it.
Canon
1. Thrawn (self-explanatory)
2. Ackbar (ditto)
4/3. Tarkin / Dooku (Tarkin is smart, but cocky and has made dumbass mistakes, the most infamous being the deathstar. Dooku too is smart, but I never found him to be more than above-average as a military strategist. Ask me for some TCW scenes and I'll provide.
5. Vader (has had crafty moments, but his recklessness and disregard for human and materialistic imperial resources bumps him down)
6. Grievous (in canon has done some super dumb-ass sh1t, but also has had his moments)
7. Sheev (what did this dude do personally to command his forces again? Aside from order 66 lol)
I only took into consideration their military capabilities not political ones.
Originally posted by MendaxPretty similar, though I would argue that some of those on your list come across even better in canon than they did in Legends- Thrawn and Tarkin come to mind.
yeah I wasn't sure if the pecking order would change in canon vs. legends so I wanted to include them both just in case.
...Though I'm probably in the minority here(especially where Thrawn's concerned.) /shrug