Never heard or seen this! Had to google it, seems impressive.
What about Wolf Fang?There are a few "run and gun" games that I'd say can enter shmupish territory, like Gunsmoke and Commando.
Fixeight y'all! After all what's better than two bodybuilder chicks making sweet love.
mjmjr speaks the truth.
Add Vasara to my list. You can tag-team the charge up attacks to alternate bullet cancels, and there is no left/right scrolling to mess up the other player's dodging.For playing verts with two players, I prefer ones where the screen doesn't scroll left/right with player movement. Try some Psikyo.
Also see Gigawing for some real cooperation-style coop shooting. Run those reflect barriers tag-team style, covering your buddy while they recharge.
This is just turning into a list of shmups. Other than Change Air Blade, Giga Wing and TSS; I don't think any of the titles mentioned here are better with multiple players.