My 'most wanted' are ranked from realistic to unrealistic. Broadly I'm trying to be reasonable, too, rather than expecting or wanting everything absolutely ideal for me.
1) Star Fox: Grand Prix to be real and coming in 2019. I genuinely think this could be a very, very good game if done right.
2) Reveal trailers for Metroid Prime 4, Bayonetta 3, coming in 2019
3) September release date for Smash, November release date for Pokemon.
4) Fire Emblem to either be a new title building on elements from Shadows of Valentia, or another Echoes title: a remake of Genealogy of the Holy War. Keeps the aesthetic and animation style from SoV. 2018 release. No ludicrously expensive season pass.
5) Metroid Prime Trilogy HD for Switch. October 2018.
6) One or two of the following: Luigi's Mansion 3, Pikmin 4, Kid Icarus Uprising Sequel, Punch-Out Switch.
7) Link's Awakening remake/spiritual sequel coming to Switch.
8) Retro Studios' second game is a StarTropics reboot: 2019.
9) EarthBound Forever/Mother 4.
This E3 is a weird one because they're keeping the focus on 2018 but there isn't that much room in the calendar - and they don't need any more big-hitters beyond Smash and Pokemon in the final four months of the year. Add Yoshi and Fire Emblem to that release window, plus DLC for games like Xenoblade 2, and I'd expect there'll only be one surprise for later this year - possibly a remaster like Prime Trilogy HD, though my curve-ball option is Link's Awakening 3D/HD cross-platform for 3DS and Switch. The original Luigi's Mansion port might come to Switch, too, though it was only announced for 3DS. Right now between first and third party I'm satisified with what Switch looks likely to have for the remainder of the year.
If they show Metroid Prime 4, Bayonetta 3 and Star Fox: Grand Prix, then that'll be more of a clue of the future line-up than we got last year (Pokemon, Prime 4). Any 2019 announcements beyond that would be surprising but welcome: I've not included it above but Animal Crossing is likely. In terms of games I want but don't expect to be announced (yet) for 2019, I'd love to see Luigi's Mansion 3, Pikmin 4, a new Kid Icarus or Punch-Out.
We should see some third party announcements: some version of CoD seems likely at this point. Ridge Racer 8 and an exclusive Tales of game might also appear.