This post contains major SPOILERS for [Star Wars: Episode VII — The Force Awakens](tag:711158).
Luke Skywalker was the main driving point of the plot in The Force Awakens. The whole story moved forward based on the fact that he has vanished. And since he was confirmed to make an appearance in the movie prior to its release, the audience kept anticipating his appearance throughout the movie, until he finally appeared in the very end... for One. Freaking. Scene.
And that scene was nothing short of beautiful! Yes, I can't find a better word fitting to describe it. The fact that Luke doesn't utter a word and yet says so much doesn't only exhibit how great of an actor Mark Hamill is, but also shows how well developed and rich the character of Luke Skywalker has become. Add that to the wide camera shot, John William's music, Daisey Ridley's expressions, and most importantly, the majestic beard, and you have the cliffhanger that made the fans more eager than ever.
However, Luke Skywalker still wasn't literally present for most of the film, but if you look at it from a certain point of view (see what I did there? No? OK), his characteristics were present in all of our new heroes: Rey, Finn, and Poe.
Rey's Strength With The Force
Most of the fans thought that it was Finn who was to become the next Jedi out of our three new heroes, but that wasn't the case. Instead, it was Rey who turned out to know the ways of The Force. What's new and refreshing about Rey being Force sensitive is that she is the first female character in the movies to clearly demonstrate and use her Force abilities. Yes, we did have Leia before her, but she never really did anything with The Force other than having this psychic relation with her brother. Rey, meanwhile, straight out kicks ass! She puts her Force abilities into good use once she realizes that she has them and manages to hold her ground against Kylo Ren. This all but fuels further speculation that Rey is indeed Luke's daughter and Darth Vader's granddaughter, something which sounds pretty reasonable considering that The Force does run strong in this family.
Finn's Righteousness And Valor
Finn started out as a Stormtrooper at first, albeit one with a living conscience. Stormtroopers have been, like everything else they shoot at, missing the spotlight in most of the movies. The main thing we know about them is that they originated as clones from the original Jango Fett, although we realize that they are not entirely clones, as some of them could be recruits just like in Finn's case. What's really special about Finn, aside from his wit, is his courage and heart. Finn might be wetting his pants in a situation, but that doesn't mean he will give it his back and run in the other direction. Although his relationship with Rey wasn't built up all that well (or at least this writer thinks), he still goes for her aid despite all the hesitation and all the odds, something that the young farmer from Tatooine would've done for sure.
Poe's Flight Skills
We all know that the pilot who took the one in a million shot that destroyed the first Death Star and brought victory to The Resistance in The Battle of Yavin was their very best, and Poe Dameron is no different. Poe is presented to us as simply as the best pilot The Resistance has to offer, something of which he gives the audience a pretty good taste. You really never doubt Poe's abilities when he maneuvers with all the TIE fighters surrounding him, and people like a character with which they feel safe and can calmly say: "Don't worry, he's got this handled". It's also worth mentioning that Poe's skills might be hereditary, as both his parents served as pilots in The Resistance and were key in bringing victory in The Battle of Endor (Return of the Jedi), as shown in "Shattered Empire", a four-issue prelude comic for Episode VII.
Bonus: Kylo Ren's/Ben Solo's Anger
Luke Skywalker and Kylo Ren are apparently very different characters, but it is Luke's father who Kylo really looks up to, and we can find one similarity or two between Luke and Anakin Skywalker. Ben Solo wasn't really shy to show that he is indeed the grandson of Darth Vader. He ultimately chose to follow the teachings of his grandfather rather than follow those of his uncle, yet he very much has this inner conflict that keeps him insecure about his choice. Anakin obviously had that conflict, and Kylo is quite frankly how Anakin should have been in the prequels, which provides more reason to compare the two. Luke also had this conflict in Return of the Jedi. We slightly see his anger during his fight with Vader signaling that he might have crossed that thin line between the Dark Side and the Light. Kylo presumably ended that conflict by passing his lightsaber through his father, while Anakin ended his conflict by disputing his mentor Obi-Wan and even led to his demise later on. Luke managed somehow to miss that train, and kept being the person that his father and his nephew once were.