The next Star Trek movie is The Untitled Star Trek Prequel (2007) (Announced)
Now this is a tough one. I will probably have to decide between Khan and Contact. A few years ago, I would have said Voyage Home, but a reviewing proved it not to hold up so well.
The Voyage Home has always been my favourite too but there's a few of them that I haven't seen in so long, my opinion might change after I watch them again.