Excellent shooters that are unpopular

[Pretas]

Triggerheart Exelica was great but people didn't take to it.

The amount of doujins and fanart would suggest otherwise. It wasn't enough to save Warashi, though.

[Erppo]

It's not just chains, should I mention destruction bonuses, weapon bonuses, merry dogs, scratching...

Except for the boss destruction bonus, every one of those is worth way too little to be required for a decent score. The dogs are especially worthless and you get a large part of the possible weapon bonuses just by using the lightning weapon at most bosses.

[nZero]

All shooters are unpopular, even the excellent ones

(Except Touhou, but that kind of popularity isn't filling up the scoreboards any faster)

[chum]

All shooters are unpopular, even the excellent ones

(Except Touhou, but that kind of popularity isn't filling up the scoreboards any faster)

http://score.royalflare.net/

[Muchi Muchi Spork]

Donpaccin

[Laurel_McFang]

There are quite a few games scattered around the place that are popular (or at least come off as well-regarded) but don't appear to get a lot of scores posted.
Cotton 2 & Cotton Boomerang (Saturn emu)
There are plenty of others too that aren't so inaccessible as some might still think.

You can sign me up for the Cotton games, but I won't impress.

Btw excellent shooter that is languishing: Kokuga Hiroshi ioshi's other output is well praised, but Kokuga has a lot to say about the genre and mechanics, it's tense with out resorting to elaborate enemies or bullet spread. Amazing little game. Probably one of the few shmuos (provided it qualifies ) on the 3ds too.

[M.Knight]

I would say the majority of portable shmups are less popular than their arcade and home consoles equivalents. Kokuga is not the only one that may suffer from its platforme of choice, and I think it is a shame as shmups on portable consoles can be very fun despite (or thanks to) the hardware limitations.
I have a blast with Bangai-O Spirits, Ketsui DS and Metal Torrent for instance.