Ironically, the SNES's SPC unit was essentially a very resource constrained ROMpler. While it was capable of synthesis like the NES (in fact, many early third party SNES titles used this, as devs migrating to the platform were more familiar with making music in this style), the ability to load samples and play them back is why so many folks hail it as the console with superior sound of its generation. The YM-2612 in the Genesis did indeed enable composers to create some legendary soundtracks of their own (Anyone who doesn't know Yuzo Koshiro's work for example might enjoy Charles Cornell's dive into the OST of Streets of Rage [1]), the best OSTs for the console were in styles that lent themselves to embrace the sound of the chip, where the SNES, leveraging the ROMpler model, allowed it to make rich music across many more genres.

Speaking of ROMplers and the SNES, these inexpensive ROMplers from Roland and Korg were what much of the music of these consoles were made on, with many of the SNES soundfonts bing made up of highly truncated versions of the ROMpler's samples. The sound of second, third, and fourth generation Final Fantasy games as composed by Nobuo Uematsu heavily used the Roland SoundCanvas SC-55, with the final title he was lead composer on, Final Fantasy 10, essentially using fully rendered tracks using the platform, with then-modern arrangement and production techniques instead of the soundfont + tracker-style music programming used on the SNES and PS1 titles (the PS1's SPU is essentially a souped up SPC700, hearkening back to its roots as the SNES CD, allowing developers to make music in much the same way, albeit with higher resolution samples, more channels, and more effects).

To your point though, the the Genesis' YM-2612, in Yamaha's OPN family was a similar chip to the Yamaha OPL-family chips used by the SoundBlaster platform, albeit it featured complex FM operators that wouldn't be seen on SoundBlaster cards until the versions with "OPL 3" chips became prevalent, which was inconsistent on the SB16 family.

[1] https://www.youtube.com/watch?v=2cx73EOaGWU