Help me choose...

[GSZX1337]

Hyper Duel! If I had to go with the list, I'd go with Eschatos.

[mjmjr25]

Hyper Duel is overpriced and relatively boring. Get Macross Scrambled Valkyrie, similar game, but better music for 1/10th the price.

From your list:
Cotton: Boomerang - Fun game, not like bullet hell stuff though
Border Down - Really neat game, not traditional, gorgeous graphically
Battle Garegga - This would be my pick. Great game. Rank, chaining, and scoring are expertly done.
Gaia Seed - meh
Ibara (!!) - very difficult game, not the most colorful cave offering, and not their best sdtrk.
Triggerheart Exelica - haven't played it enough to critique
Bullet Soul - meh, well done, but it won't hold up as a classic, once you get past the impressive graphics, there isn't much to this one, scoring is straightforward, boss fights are too long, gets boring in a hurry, stages aren't difficult at all
Eschatos - haven't played it yet

I'd go Garegga.

[Spyke]

Thanks for replies.

Also if there are any other recommendations out there I'm happy to hear them.

Ant

[rufus777]

.

[GSZX1337]

Hyper Duel is overpriced and relatively boring.

WHAT!? Hyper Duel rocks, man. I will agree that it is overpriced which is why I burned a copy.

[Chempop]

Battle Garegga is by far the best game on your list, but it's brutal! My second choice would be Eschatos. It might even be best as your first pick because it has a wide array of modes and difficulty settings, and also includes 2 retro game. Heck, isn't there even a double pack with Eschatos and Ginga Force? If Garegga wasn't on your list it'd be a no brainer.

Hyper Duel is overpriced and relatively boring.

WHAT!? Hyper Duel rocks, man. I will agree that it is overpriced which is why I burned a copy.

I'm going to have to agree with Mike here, I was hugely disappointed with hyperduel, sold it and went right back to thunderforce 3, 4, and 5. Never looked back.

[nightrnr]

Strongly seconding the suggestions of Cotton Boomerang. Any problems you had with Cotton 2 have most likely been addressed in Boomerang. You can now shoot while holding sealed enemies, you now have tail shots to cover your backside, no having to beat the game to unlock command shot button mapping... best of all though, no more shooting those stupid crystals to get the color you want. That last tweak alone makes Boomerang the pinnacle of the series.

Concerning command shot mapping: there's a pretty simple code to get to that menu option without beating the game.
Also happens to be the one and only contribution I have made to gamefaqs; at least as of now :

http://www.gamefaqs.com/saturn/574730-cotton-2/cheats

I think I like having a life bar in Cotton 2 better than the other improvements in Boomerang. But that's only so far, as I haven't played Boomerang much yet.
Most Cute-em-up fans will likely prefer Boomerang.

[DocHauser]

Eschatos also contains Judgement Silversword and Cardinal Sins, doesn't it? That makes it pretty essential, I'd say.

[Spyke]

Yep that Ginga Force/Eschatos pack looks good value for money. But are they groundbreaking/otherwise memorable games?

Ant

[mjmjr25]

Both are good and imo deeper than Bullet Soul. I don't know that either will be remembered as classics, but you'll put hours into each of them.

However, there is a classic on that compilation, JUDGEMENT SILVERSWORD is an add-on if you will. (full game, of course). It also has CARDINAL SINS.

For $75 you'll get your monies' worth. Silversword is only available elsewhere on the Wonderswan Color handheld system and goes for $130-ish CIB.