Here is an archive of all the past top five lists I've done over the years.
Everyone knows that What If...? comics often end up with generally sad endings (like Spider-Man joins the Fantastic Four, but ultimately it leads to the Invisible Woman leaving the team to be with Namor or the Hulk having Bruce Banner's intelligence that leads to the Thing ultimately becoming a mindless savage) or outright sad endings (lots of them end with pretty much the entire cast of the comic dead). But what about the ones with HAPPY endings? Check out the top five What If...? comics where everything actually turned out okay!
What if Daredevil Became an Agent of Shield?
What If...? #28 (by Mike W. Barr, Frank Miller and Klaus Janson) ends with Matt Murdock being an accomplished agent of SHIELD and even saving his father's life! It's only a little bit low on the list because of the relatively low stakes of the ending...
What if Elektra had lived?
What If...? #35 (by Frank Miller and Terry Austin) ends with Matt and Elektra (who was not killed by Bullseye) running away together...
Again, somewhat low stakes, but still, great issue.
What if Rick Jones had become the Hulk?
What If...? #12 (by Don Glut, Sal Buscema and Bill Black) has Rick Jones, as the Hulk, still end up becoming Captain America's new Bucky and then sharing a body, sort of, with Captain Marvel. Just like in the original comics, Rick would be in the Negative Zone while Captain Marvel was out doing superhero stuff. However, while Rick was in the Negative Zone, Bruce Banner and Reed Richards figured out a plan where they could split Rick and Hulk in the Negative Zone...
Everything worked out for Rick and the Hulk became the champion of the Negative Zone!
What if Spider-Man had kept the Captain Universe powers?
What If...? #31 (Vol.2) (by Glenn Herdling, Scott McDaniel, Tim Sanders III and Sam De La Rosa) has Spider-Man keep the Captain Universe, which ultimately causes him to run afoul with the Avengers, who are all, "Dude, absolute power corrupts absolutely!" and Doctor Doom, who is all, "I was to be corrupted absolutely!"
Doom DOES kill the original human host of the Uni-power, but after that, everything goes well for the world...
Spidey DOES lose his powers, but come on, dude unifies the world! That counts as a happy ending!
What if the Illuminati's rocket carrying Hulk hadn't been knocked off course?
What If...?: Planet Hulk #1 (by Greg Pak, Rafa Sandoval and Gary Erskine), we see what happened had Hulk landed on the peaceful planet that the Illuminati intended for him to land on. Well, as it turns out, things went well!