There are numerous products out there fighting for market shares. In the end, they basically all do the same thing, sometimes with a different twist, sometimes with no difference worth mentioning. For many organizations, it has come down to choosing a backup product based on a single feature or a cultural fit (i.e.: Sun + Veritas).
Without wanting to bash the smaller players, I would personally make my backup software choice based on the importance of the installed base. Not to say that the most sold software is automatically the best. However, the more a product has users, the more you will find user groups, forums, cross vendor support, etc. Hardware vendors also tend to qualify the most popular software first.
For the above reasons, I would list my preferences (alphabetically) as being the following solutions, for both their features and their installed base: CommVault Galaxy, IBM Tivoli Storage Manager, Legato NetWorker, Veritas Backup Exec and Veritas NetBackup.
Read W. Curtis Preston's answer to this question.
This was first published in June 2004