There is no doubt this game is very similar, but not a clone. They didn't take match character fighting style with different faces in different backgrounds. There isn't a Kirby like character, a Samus like character, a Hyrule like level, etc. They made their own stuff.
Here are some differences:
-Jumping in PSASBR is less floaty while faster and higher
-PSASBR has a dodge mechanic, on ground and air that works on attacks and specials
-No health bars, kills are done by 3 unique special attacks, no one can steal your kills by standing back
-Offense is required always, defense is to be mastered
-AP is gathered from attacks and orbs found on the level, fills your special gauge
-Attacks utilize three buttons, Square, Triangle, & Circle, each having a normal, a forward, an up, and a down attack
-Some attacks work into combos
-Grabs have a forward, an up, and a down attack
-Characters have a baseline of 18 different moves including specials, some characters have more, i.e. Toro
-Some specials can be dodged, some interrupted, Kratos' level 1 super stabbing forward with the sword of olympus can be interrupted by a quick attack early in its execution (before the lunge)
-Moves are very interesting/unique, Kartos' has a charge with his shield and spear, the shield actually blocks during the attack
-Levels evolve and expand, the Uncharted Cargo plane starts in the cargo hold before opening and falling out the back, the parappa dojo level is in the small dojo before the walls break down and you are in the city, environmental dangers exist, mash up levels, Buzz trivia questions
-From what I've gathered SSB didn't have a solid online structure, though it still had one, PSASBR has a well developed online component with the perks of PSN.
-Scores are based on kills and deaths. 2 points per kill -1 per death
Before the PS3 everyone was nice to me :(
