I've been playing Ultima Online for over a year now, and even though it has outdated graphics, it is still the number one player versus player game I have ever came in contact with. I wasnt fortunate enough to start when OSI came around, but because of a few friends of mine, I happened to find a nice freeshard. This freeshard is called Metropolis. If anyone knows alot of Ultima Online, it is a Pre-UOR shard, that takes the 99' era of PvP. It currently is rated #5 on the top 200 list for Ultima Online. Here is a link to the Top200.
If you are looking for a nice playerbase, with a variety of people including PvMers, PvPers, and RPers, then I HIGHLY recommend taking a look at Metropolis. The offical website is: http://www.metropolisshard.com/index.php
We are currently in the process of revamping the website, and making a Flash Intro to it.
So if you are a Ultima Online lover, or you just want to try something new, come to Metropolis. Here is a link to how you can setup and play for free.
And here is a guide to the basics of Ultima Online.
Thank you, and have a nice day.