I’ve seen all of what exists, other than The Invasion and The War Games in full (but I have seen clips of the important bits). He’s definitely great in his own right, but he has a different sort of presence to him. I’ve previously stated he’s my favorite of them all, but after revisiting Hartnell’s era recently, I really enjoy his characterization. It’s a shame that whenever they want to try to go back to it, it doesn’t fare so well with viewers (Colin Baker, Peter Capaldi).
Hartnell made his presence known, Troughton disguised his cunning into foolishness. But both are great. Of all the eras, the 60s are what I’d most want to rewatch.