I'll answer this in a few parts:
SSF2 - I don't watch too many SSF2 games to be perfectly honest (I play them lol), but I'll list a few characters/players I enjoy seeing:
Proto's Goku, Lite's Sonic, Rev's Falcon, Zalo's Zelda, DescendedSun's anything, Aegis's Fox, Masky's anything and Rem's Tails. I've either seen stuff by these players or played against them, and really found their characters/playstyles in general really impressive, or seen a combo video of theirs that really impressed me.

Smash - I'd do this by game as well, but the simplest I can go with is:
Melee - It'd be a tie between S2J, Wobbles, Fly Amanita and Bizz. S2J's Johnny stocks are frankly a sight to behold. Bizz is sheer entertainment value, and Wobbles and Fly do so much cool stuff with Icies, it honestly gets me hyped when I see a set from them.
Brawl - Mr. R - There's a hell of a flashy gif of Mr. R. performing a shieldbreak on someone's ZSS. Now that's certainly different from the nonstop planking otherwise.
PM - Chudat - Do I even need to say anything?
Smash 4 - Dath/Nairo and any PAC-Man main (Zage/Abadango/Beatfox etc.) - I may be biased on this one, but Dath and Nairo's Robins are really good, and really show what the character is capable of. Additionally, Nairo's other characters (Pit/Dark Pit especially) are really fun to watch. PAC-Man is also incredibly interesting to watch, and players who utilise the item game and traps really well are personal favourites of mine.

As for other "real fighting games" ( ) I play Street Fighter II and Street Fighter IV. Because I'm a total scrub at Street Fighter II and I can't find anyone else I like playing as much, I alternate between Ryu and Ken. I don't play SFII competitively, but I instead use the game for tournament mode to improve my fundamentals a bit. Originally, I tried using Ryu in SFII to help me in Smash, but now my experience in SFII has actually hindered me, as there are combos I would be able to do in SFII that I can't do in SSB4.
In Street Fighter IV, I play Volt (iOS version of SFIV) because I don't have anything else to play it on. Because of Volt's online multiplayer, I do play competitively, and I main Dee Jay, simply because everything about Dee Jay screams "Fun", and he's a fairly easy charge character to learn as most of his inputs are either Charge Back -> Forward -> Punch/Kick (Air Slasher/Double Rolling Sobat) or Charge Down -> Up -> Punch/Kick (Machine Gun Upper/Jackknife Maximum). Additionally, he has a lot of versatility as he can play a rushdown game or a zoning game without too much trouble.

Apparently, he's also a low tier as well. Whaddya know?