Most needed for what? Personal knowledge, employment opportunities, technical competence...?
Most of those that you listed are pretty outdated. For example, I think you would find it impossible to become ceritified in Solaris 2.4 these days...

I think the answer is that you should be certified in what you need. Most good employers will send you to the training classes anyway if they relate to your job. Get certified in what you will be using (or plan to use), then pick up any others later if you think they will enhance your resume. IMO, most Unix systems are similar enough that a certification in any of them will look good to a potential employer...

Most big Unix shops are probably running Solaris, HP-UX or AIX as their primary systems...become comfortable with one (or all) of those and you will be good to go.