AstroEmpires is really good, but I had to stop after a couple years because it was so much of a time sink. Especially when a Server War would break out that would last for weeks. I had to schedule my sleep based upon when my fleets would arrive to their destination, then coordinate attacks, always needing to be ready to abort or move at a moments notice. It was fun, but damn what a commitment.
The only Browser game I play now is Hobowars, which someone here started a thread on almost 9 years ago and who I joined from.