Use a little WD-40 on the strings before playing. Pour a little on and work it in. Not too much. It'll be better than the standard string-ease products and it will clean your strings.
Some say it gums up the strings. Not in my experience. It's not a popular idea but it works for me.

Also, loosen each string slightly (about a whole step or more) and snap it against the guitar. It snaps life into it.

Brand new strings don't always sound the best. Sometimes it takes a little playing-in period to make them sound good. Re-tuning new strings is no fun either.

There is a difference in the way certain strings sound. I've heard otherwise but don't believe it.

Some will retain life more. A lot has to do with the guitar itself. The strings have to be a good match to the instrument. I've tried different brands with different instruments and some will not work well with some instruments even if they are high-priced strings. Sometimes even Black Diamonds will make some guitars sound good.

Don't believe the hype about guitar strings. They have to fit the instrument.

Frank