It really is quiet sad that games with great soundtracks never see official soundtrack releases. Of course many OSTs never get released in the states anyway, but that's a whole different blog entry. Banpresto's SD Great Battle series (for those not in the know, SD stands for super deformed) is a line of Super Famicom games that mixes the popular Gundam, Ultraman and Kamen Rider (Masked Rider over here in America) and is one of the many game series that has no official OST. I've never played these games but thanks to a fellow forumite and video game music lover, I was able to hear the incredible music. It's fantastic listening and offers something for everyone.
The SD Great Battle games had five main titles with several spin offs. My friend was kind enough to upload all of them. Do yourself a favor and download these. You won't regert it.