I'm going with Stranger Things for several reasons.
1) JW: wasn't a flop but it didn't do nearly as good as the first one. There is no buzz around this movie and I honestly think no one really cares to see another. They have made 5 or 6 of these movies. There is no buzz. Lets also admit there has been more than one JP pinball games already where is the buzz for another one over another title worthy of Comic Con coverage.
2) Stranger Things: Despite the fact I'm not a fan of the TV show, a lot of people are and the TV show has a lot of buzz. The new series just came out which NetFlix would totally embrace at comic con. No one has ever made a Netflix pinball game so this would be a first, that is buzz.
3) Elvira: She's really old news in Hollywood and the comic con audience. I'd go with no chance here. Elvira is popular pinball title but not worthy of comic con reveal.
4) Music Pin: No chance you would debut that at comic con unless it was Queen which had a recent movie. Zero Chance.
I'm going with Stranger things 110% because of the reveal location. There is no new JW movie being promoted right now and wouldn't warrant a comic con reveal. Stranger Things is a hot comic con title.
I'm going with Stranger Things NOT JW.