The best choices would definitely be the F-15 Silent Eagle and the PakFa (
if it performs as anticipated). However, the F-35 will definitely get the award. Guaranteed. Too much political momentum going on, and unlike Canada there's not sufficient domestic political/technological opposition against the F-35. The F-15SE doesn't have the same level of clout, which is unfortunate since the F-15Ks that the Koreans have have proven themselves as some of the most sophisticated F-15s out there. The F-15K is arguably the most advanced F-15 in active service, although the Singaporeans with their F-15SG can also lay claim on that title. Thus, selling the F-15SE should be easy, but due to the great political need to make the F-35 a 'success' there is no way the SE will win in Korea. As for the PakFa ...even
if it somehow the thing is the best thing for anyone who can't get a Raptor, there is zero chance of the Koreans choosing it. The PakFa being a contender in the Korean contest made some noise a couple of years ago, but it was never really going to happen.
Too much pressure for the Koreans to select the F-35, which is quite bad since the F-15SE would have been a better choice for them, with the savings going towards their own indigenous stealth fighter project. Already the F-15Ks are FAR more than sufficient to anything the North Koreans can wag at them, and as for China the SEs would be sufficient, and any Sino action would most probably bring in other regional powers, with Japan and the US being the most likely participants. Thus, no real need for the F-35.
But it will win this contest.