Solaris struggles against Linux, but it wasn't Linux that killed Solaris - it was Oracle.
Solaris could stand by its own merit. It was backed by a huge technology company (Sun Microsystems), it had the world's most advanced file system, it had great technology such as DTrace, etc.
It was active and had great community participation through OpenSolaris.
Sun was highly regarded in the technical community due to being a huge supporter of open source. Java, OpenSolaris, NetBeans, OpenOffice, VirtualBox and lots of other software. Not to mention open source hardware through the OpenSPARC project.
Then Oracle comes a long, buys Sun and manages to fuck every single thing up.