1. Ultimate
The best Smash game, yes. I love all of the amazing characters, the expressive art style, and spirits. Trophies were nice and all, but spirits are really fun. I love all of the DLC, and I love how the roster is insanely packed. It was amazing, and a great improvement compared to Smash 4. The solo content was improved, and the style was improved overall. My main issue is the online, it is atrocious. It is a major step down from For Glory, and For Glory was pretty flawed. Also spirits should have had descriptions, but I consider that only a small flaw. Either way, I love Ultimate.
2. Smash 4
The Smash game where I REALLY got into Smash. Cloud was fun as hell to play, and I remembered beating all of my friends with Cloud and angering them. Sometimes they would not even let me play Cloud. Anyways, it was fun. The characters were nice, and the atmosphere was smooth. The artstyle as a major improvement from Brawl. My issue is that the solo content was butchered from Brawl, especially on the Wii U. Smash Run would have been cool for the Wii U. Also getting trophies and other items felt too randomized. Rolling and air dodging was too safe too. Overall, I loved it.
3. Brawl
A game for the newcomer. It is fantastic in terms of solo content. Subspace Emissary was so awesome to me. Seeing all of these characters from different games have nice interactions was fun, even if they didn't have much dialogue. I kind of wish Ultimate did this, but I am fine with what we got. My issues with it is the slow and floaty nature, and the artstyle doesn't fit all that well.
4. Melee
I have played this game in the past before, but I'm just not skilled enough to dive myself into it. I used to be pretty into competitive Smash, but now its just not my thing. It is pretty fun though. Not much to say, because I didn't really invest in it that much.
5. Smash 64
This is my least favorite Smash game, but you know, I respect it. It seemed nice for its time. I am not going to go into much detail on this, because I only played it for a little bit.