What If...? #10 (by Don Glut, Rick Hoberg and Dave Hunt) had one of the biggest cop-out endings, but not before it was very cool seeing that had Jane Foster become "Thordis," well, not much would have changed. She was actually a good Thor, just like how she is currently a good Thor. I like that. Anyhow, in the end, the original Thor returns and Glut pulls a major cop out move to give everyone a happy ending...
"Oh yeah, Odin is not married in this reality." Hilarious! Still, I dig the happy ending.
4. What If the Fantastic Four's Second Child Had Lived?
What If...? #30 (Vol.2) (by Ron Marz, Rurik Tyler and Ian Akin) was the second of two stories where the second child had lived. The first story was your standard "everything goes wrong" tale. The second one, though, has her grow up to become a healer and a voice of unity for the people of the world. The government tries to assassinate her, but instead, she survives and cures all of the distress...
3. What If Jessica Jones Had Joined the Avengers?
What If...?: Jessica Jones Had Joined the Avengers #1 (by Brian Michael Bendis and Michael Gaydos) sees Jessica decide to take the Avenger and SHIELD up on their offer for her to be a superhero liaison between SHIELD and the Avengers.
She' so attentive that she figures out that Scarlet Witch has some problems, so she helps head off Avengers Disassembled years before it took place.
Then she and Cap end up getting married!
I guess you argue that this didn't work out for Luke Cage and Danielle Cage, but otherwise, it worked out pretty well.