Token Ring is a very old and outdated LAN protocol in comparison to Ethernet. If I remember correctly, Token Ring was developed years ago by IBM, after which the IEEE committee made it a standard. Speeds of up to 16Mbps are possible with Token Ring networks, providing safer methods of data transfer between nodes when compared to Ethernet.
In fact, despite the Ethernet fanfare, a recent IDC survey showed that there are over 22 million nodes world wide using Token Ring! Moving to technologies such as Ethernet/Fast Ethernet is not straight forward for most companies who have developed their network applications around the Token Ring standard (i.e. larger frames than Ethernet), meaning that an Ethernet installation would surely mean they'll have to fork out a lot more money in the long run.
Ethernet on the other hand is pretty much a standard everyone is happy to settle with. Its rapid market acceptance and growth have been the driving force to constantly get new products that would support fast Ethernet speeds, bringing the speed barrier to the 10Gbps mark!
Initial installation costs of Ethernet are much less when compared to that of Token Ring, and you've also got a wider range of products that work with Ethernet as its pretty much today's standard.
In the long run, follow the market, Ethernet has its problems but its constantly evolving and getting better.