Warning: Really long-winded speech ahead. Read at your own risk:
It really depends. Luke from anywhere before ESB would definitely not stand a chance, since he has had very little formal training. However, after training with Yoda, Luke's skills were far greater, and by the end of ESB, I believe he would definitely at least stand a chance, though likely wouldn't be able to score the victory. Luke from RotJ or later would almost certainly be able to defeat Starkiller. I came to this conclusion using several obvious and widely accepted facts. First, Starkiller's duels with Vader were always immensely difficult, and he barely pulled through both times. During Galen Marek's duel against Vader in TFU, even with Marek's best use of form III, he sustained constant injuries from Vader's assaults, only managing to defeat the Dark Lord by goading him with various taunts until Vader lost his cool and got sloppy. In Starkiller's duel at the end of TFU II, the novel states that Starkiller was actually unable to best Vader in single combat, and had to deceive him instead. By RotJ, Luke had greatly surpassed Vader. Go ahead and rewatch Luke's duel against Vader (
http://www.youtube.com/watch?v=_RFYoZ7H67A). Vader held nothing back (As evidenced by his repeated attempts to kill Luke whenever Luke dropped his guard, slashing straight for Luke's head when Luke deactivated his lightsaber). And yet, in the first 8 seconds, Luke was able to completely overwhelm Vader with relative ease. The only time Vader ever had Luke on the defensive is when Luke simply calmed his nerves and lost the will to fight. For the rest of the battle, Luke was completely, 100% in control. And even when Luke had lost his will to fight, Vader still couldn't come close to landing a single successful strike. This means Luke definitely has the edge on Starkiller as far as lightsaber combat goes. Luke is insanely adaptable, and is definitely not easy to intimidate (He took down a f***ing Rancor. I doubt Starkiller's aggressive attacks or dual blades would spook him much). Also, thanks to journals left in Ben Kenobi's hut, along with his instinctive knowledge from the duel on Bespin, Luke has a vast knowledge of lightsaber forms, including knowledge of forms II, III, V, and VII. And to top it all off, Luke's learning curve is out of this world! Watch his first fight with Vader on Bespin. For the first few moments, Luke is totally outclassed. But as soon as he gets his second wind, he's completely adapted to Vader's style, and is then able to overcome the Dark Lord of the Sith himself! Vader had to resort to Force-based assaults and a complete change in his fighting style (Shifting from a heavily form II and form V influenced style to pure form VII, giving up all sense of defense for an absurdly overwhelming offense) in order to defeat Luke in ESB. And even after using everything he had against Luke, the completely inexperience duelist actually managed to land a successful strike on Vader's shoulder. Luke managed to land a blow on the most deadly Jedi hunter of all time, in their first encounter, with little experience! Had that been any other duelist, that strike would have literally disarmed them, if not killed them instantly. It was only Vader's durable armor that saved the Dark Lord. Starkiller, for all his skill, simply would not be able to match that level of instinctive natural talent. Any new trick he could throw at Luke, Skywalker would quickly adapt to and counter in some way. Then we come to the Force based aspect of their duel. Luke's skills in the force by RotJ have been greatly underestimated, even by many Luke fanboys. In ESB, during his training with Yoda, we see Luke has extreme talent with telekinesis, able to lift several different objects and balance various rocks with perfect precision. Sure, at that point, it took quite a bit of concentration to pull it off. But by RotJ, I'm fairly certain that level of precision would be a simple matter for Luke, requiring no real thought or effort. In the beginning of RotJ, Luke yanks a blaster from a man's holster in the blink of an eye using the Force. This is the fastest they've ever shown an object move as a result of the Force, discounting Sidious' duel with Yoda. In every other instance in the Star Wars movies, whenever an object is telekinetically moved, it rumbles for a second in its place before accelerating toward it's target. In this case, there was no brief moment where the blaster started to get tugged. It simply flew from its holster into Luke's hand, without Luke having to give the blaster a moment of concentration beforehand. At first, I just ignored this little incident, but after seeing the way he effortlessly hovered C-3PO in the Ewok village, showing no signs of effort or fatigue on his face, and with barely a split second of concentration, I realized it was entirely possible that Luke's Force talent had already reached a level in RotJ that surpassed any established Force user other than perhaps Sidious himself, as far as the movies were concerned. With that in mind, I'm completely certain RotJ Luke could withstand any telekinetic assault Starkiller threw at him. After all, Starkiller's telekinetic assaults weren't exactly that powerful, even in the extremely exaggerated games. Vader and Sidious were both able to shrug off Starkiller's telekinetic assaults as if they were nothing. (For the record, any idiot who tries to say "Starkiller pulled down a Star Destroyer," let me just tell you... That is total BS! According to the novel, the Star Destroyer was already falling, and Starkiller just BARELY managed to redirect it so the ship wouldn't land on his head. And after redirecting it, Starkiller was so drained that he collapsed from exhaustion, and it nearly cost him his life. Another fact worth noting is that Starkiller did not truly defeat Sidious. After all of Starkiller's attacks, Sidious is the one who walked away unharmed, while Starkiller's corpse lay smoldering on the floor. Meanwhile, post-RotJ Luke managed to defeat a clone of Sidious, which was in its physical prime, and was stronger in the Force than ever before.) Leaving Starkiller with only one weapon, Force Lightning. And as the games' bosses proved, Starkiller's lightning, while immensely powerful and destructive, can be blocked by a lightsaber. Given Luke's immense talent with a lightsaber, it would be a simple matter for him to defend against said lightning. I can therefore say, with complete certainty, that RotJ Luke would definitely stand a fighting chance against Starkiller, and could conceivably pull off a win with little effort. Any version of Luke after that would just be overkill. Please, if you disagree in any way with a single thing I just said, try to come up with a logical argument. I'll admit, Starkiller is powerful, and if I'm overlooking anything, it'd be nice to know. Though I am fairly certain with my analysis.
