I suck at traditional fighters. For the longest time, I couldn’t comprehend how the controller inputs would work or how the neutral game played out. Smash appealed to me because it was familiar in gameplay, focusing on the platform genre as a backbone to the mechanics. When Snake and Sonic were added to the roster in Brawl, many people exclaimed how characters like Ryu could work in Smash. Despite that, Sakurai went then on record and said that he didn’t see him working because he was from a fighting game already. Then, Smash 4 had DLC, and what do you know, Ryu is in it, almost functioning exactly like he did in Street Fighter.
I find the inclusion of Ryu and his moveset in Smash 4 very interesting. I see it as helping both Smashers and traditional fighter fans learn each other's games while still allowing them to feel comfortable playing Smash using Ryu. His specials can be played out normally in Smash like any other character, allowing common fans to still enjoy his moveset; however, on the Custom Move input screen, it shows off that Ryu can do stronger versions of his specials with the same input methods as in his original game.
Smashers were quite baffled on how to execute this difficult tech skill.
The way Smash 4 illustrates these inputs is outstanding and quite simple. It does this by showing the kind of motion the player needs to do with the control stick (a quarter circle, for example). Not only that, Ryu’s gameplay style focuses on spacing and combos alone. Every single one of his moves is straight from Street Fighter, even all the way to his animation used for countering, which acts as his power shield. Also, Ryu has weak and strong variations on all his ground based tilt attacks, further showing another thing Smashers can learn. This teaches them not only the kind of inputs Ryu can do, but also the basic gameplay of Street Fighter, focusing on patience and attentiveness to detail.
Ryu’s design also helps SF fans from not becoming too alienated to Smash. They can play Ryu and still do the same moves, but the game also requires them to rethink the effects of their inputs. The first thing they will instantly notice is the difference in momentum, where attacks make characters gradually fly farther and farther instead of a set distance on some moves due to the percentage display. Then, they will take note of the button count, where there are only a few buttons for them to input Ryu's moves. Finally, they will then notice the scale of everything when it comes to the stage, knockback, and neutral. Thus, they can’t play Ryu 100% exactly like they would in SF, but with the comfort of already knowing the basics of Ryu helps ease them in the gameplay Smash offers.
In short, I welcome Ryu’s inclusion in Smash. It has made me not only interested in playing Street Fighter and learning the controls for that game, but also the other side of the fighting genre.
TL;DR: Ryu brings Smash fans and Street Fighter fans together like two sides of a coin.