Personally, I like Evil Dead the best. It’s got that lightning in a bottle feel of folks genuinely trying to make a harrowing horror movie and getting comedic undertones. Nothing is more horrifying to me in the trilogy than that initial Shelly dismemberment scene. Evil Dead is raw filmmaking at the hands of an extraordinary then-19 year old talent. In many ways, Evil Dead II is more refined, but, as a result, less visceral and spontaneous.
Of course, I still love the rest of the trilogy, as well as the Ash v. Evil Dead TV show.