Actually, that is correct. It seems you never got to the last levels. But perhaps you remember the beginning where all these fish/dolphins get sucked up in the air? Spoiler alert: it was the aliens, and Ecco eventually travels to their mothership to kick some butt!
There are only two Sega games that my friend had that I recall: Sonic and Ducktales. Or maybe Ducktales was on the NES. Either way, games like these I largely only know of.
I’m afraid I don’t know them other than what’s covered on LGR.