Not every IP gets a long, guaranteed life filled with fame, fortune, and spin-offs. There are far more Gex-es out there than Marios. But, that doesnt mean the series that died off are bad or less deserving. Some of them are both fan favorites and critically acclaimed. They just, well, didnt make enough money or ended up lost to time.
Source: N4G PC Top 7 Dead Video Games (That Should Rise Again)