Symphony is a physics game involving music:

http://www.phyfun.com/Games/1-9211-Symphony.aspx#.VdIm4peic4k

I'd honestly showcase anything you've made. As you said, you consider yourself a sound designer and not a game designer. If anything, it would show your resourcefulness and enthusiasm for sound design; that you'll even create small games to show off your sound design skill. If this is for a portfolio I'm sure any prospective employers will be listening to how the sound has been designed into the examples anyway.

However, this is not to dissuade you from making more games! I just feel you shouldn't be afraid to show the hard work you've accomplished already.

In terms of more game ideas, I honestly feel you should study game design on at least a basic level. The core concepts of games design help you find games in anything! I recommend the book 'Challenges for Game Designers' by Brenda Braithewaite and Ian Schreiber.

http://www.amazon.co.uk/Challenges-Game-Designers-Brenda-Brathwaite/dp/158450580X/ref=sr_1_sc_1?ie=UTF8&qid=1439840141&sr=8-1-spell&keywords=challenges+for+fgame+deisgners

I feel the first few chapters would be particularly invaluable to you, for any of your game ideas large or small.

Hope this helps.

Valoon: if you insist on making a game, get ahold of me sometime. I'd be willing to trade programming for sound work on an hour-by-hour basis, if you're interested.

an aggressive science-fiction game with alot of special effects, attacks and explosions......stuff that demands sound design and sfx

check out the music of Sonic Symphony for inspiration as well as Attila Ats - Shredder

Trailer music is perfect for finding sound effect driven music