Dramatically. Go play Smash 4 and you'll see.

Everything is much faster, knockback works in a fundamentally different way. You can use any move out of a dash, meaning dashing in general allows you far more options than it ever did, and aerial moves as a whole have had their landing lag reduced, meaning it's safer to use them. Dodging has been completely revamped, with new mechanics punishing you for rolling too much, and lots of lag on airdodges, which by the way can only be used once per jump, unlike in Brawl/Smash 4 where they could be simply spammed. There's now clear indicators for how close you are to the blast zone when thrown offscreen, or for the current status of a specific character gimmick, such as Cloud's limit or Robin's tomes. Perfect shields have also been completely changed, now functioning very much like a parry, activating if you release the shield button at the right time rather than pressing it, and directional airdodging allows for several different movement options that weren't possible before. Furthermore, there's a new mechanic where a character will break free from a grab if you press grab at the right moment, and techs have been fixed across the board (in Smash 4 there were many untechable situations, such as when you're footstooled into the ground or get hit by a random spinning animation). It also seems SDI isn't as effective as before, and DI as a whole might not work the same way. Of course, that's not even getting into the characters specifics - with minor and major changes to most moves in the game, I could go on for hours here.

"Oh, but it kinda looked the same, it's a port".

people that have played it said its feel like smash 4, in fact the same winner of the smash 4 tournament, won the smash 5 at E3.  

people that have played it said its feel like smash 4, in fact the same winner of the smash 4 tournament, won the smash 5 at E3.  

in the end of the day its looks like a iterative sequel, many pros that have played it say its smash 4.5, and many think its' a port based on the long gameplay presentation, it's not something thats blowing people away like mario odyssey and zelda BOTW.

That is primarily anecdotal on your part, I can easily bring up plenty of people that see it as a new game with substantial gameplay changes (in fact, the pro Smash 4 player that won the tournament said the game was quite different compared to Smash 4). Beyond that, Mario Odyssey's concept is not totally new either it is very much an iteration of Super Mario 64, Sunshine, and there are even elements from Galaxy and 3D World. We have also had games like Splatoon 2 which have very similar relationship to their predecessors that Smash Ultimate is having with Smash 4 and that game helped maintain momentum in the West and actually move a substantial number of consoles in Japan.

For me Smash Ultimate is just as much of a new entry as its predecessors (as a fighting game, that generally retains its style from one version to another, there is a limit on how much it can evolve), but lets say, for the sake of argument, that the majority of gamers see it your way in that it is a port. Well lets look at games like Mario Kart 8 Deluxe, which is a port, being both an evergreen title and a system seller. On other systems you have ports like The Last of US on PS4 and GTA V on PS4/XONE, both of which moved systems and sold well despite being ports. There is also the Switch's portable factor here, where games of this level from Nintendo where simply not possible on their previous handheld (Smash 4 on 3DS was substantially compromised compared to the Wii U version for example) so for many 3DS owners (where Smash 4 was mostly purchased on) this will be a substantial step up. Finally, BoTW was also available on Wii U, yet it drove Switch sales.

Just based on past precedence, Smash Bros and Pokemon Let's Go are both big and they will move large numbers of systems and the games themselves will sell quite well overall. The only thing in doubt here is whether or not they will be enough to move 20 million units this fiscal year. Personally, I am seeing Switch being between its first full fiscal year and the 3DS's second full fiscal year (13-15 million). For me the only way I see them approaching 20 million is with a price cut on the stand alone models in addition to bundles at the current price. 

umm because the hyperbole is ridiculous, all i been hearing since last year is switch will destroy everything during the holidays with mario, holidays come, and switch gets out sold by both consoles. Then In 2018  switch will win almost every NPD, switch only wins one so far, and now the hyperbole smash and pokemon are the second coming, yet when the pokemon came to 3ds in 2013 holiday sales were weaker then the previous year, same with smash, on wiiu, and 3ds.