Can't beat the original and the one-and-only Leonard Nimoy for this. Nimoy put a ton into the character, with interviews and articles explaining why Spock did things the way he had. (e.g. neck pinch because he didn't want to zap lasers or be a generic bar brawler throwing punches.) Nimoy was iconic in acting and giving Spock depth, building up quite a lot. When the inevitable and obligatory "Which of these twenty actors played Worf the best", there's only one answer there as well: Michael Dorn. For the same exact reasons: Dorn took what little was on paper and put a ton of effort into making something special out of the character. Indeed, his inclusion into DS9 was the best thing that could happen, but before I digress... Ditto for Tim Russ as Tuvok when compared to the six hundred and seventy-three other actors who'll get to do the role eventually, since VOY expanded on the Vulcan species and lore, with Russ making the presentation iconic. Neither Nimoy nor Russ can be improved upon. Just mimicked at best. Mishandled at worst.