Anyone else really underwhelmed and disappointed by the tease and announcement?

You shouldn't be. SEGA made it very clear it was "classic" focused and limited in its appeal. I dont blame you guys though, I dont Altered Beast in my collection either, but if you expecting a new IP or entry into a classic series in a less than hour 24 tease (what big announcements are made that way) then you set yourself up.

Nothing About the tweet suggested a massive announcement. 

A caballo regalado, no le mires el dentado.

It's not a major release, but what can you do? I would have liked som JRPGs like Snatcher or Langrisser (the originals, not Reincarnation Tensei, that one is awful), but better this than nothing, I suppose.

Yup. Snatcher, Eternal Champions CD, Ground Zero Texas, Planet Harrier and Boogerman. 

You guys do realize this is a compilation of 3D Classics already released on eshop correct? All those games both of you listed have not received any 3D remake treatment thus obviously wont be included.

I know, but wanting things is still free. :P

Yeah, but they didn't know this before they revealed this. I think that they were stating what their hopes were prior to the reveal. Personally, I think that 9 games is way too few, especially after how many were in Sonic's Ultimate Genesis Collection.

This 

This too. 

Since the days of the PS2, I have bought shit tons of Sega collections. With the reboots, remasters and remakes I genuinely thought this announcement was going to be something different than just another collection. This feels more like recycled news as supposed awesome news some of thought it would be. 

Japan has 3 3D compilations based on each batch. SoA will probably be attempting the same thing.

Again these compilations are based off what is available on eShop. There are nowhere near the amount of 3D classics to have as many games in ultimate genesis collection.