That depends. If they don't hold any cherished memories for you, and you want to make a few bucks, selling them is the way to go.
That isn't always easy, though, especially in today's market.
However, certain cards may be valuable, such as "star" rookies, and they'd be gobbled up quick.
It all depends on what you have, the era, the sets, the players, etc. all determine the values.
My suggestion is to go through all of them, and create a list of the year, manufacturer, card number and player...along with any additional attributes that stand out...and once that's done, research them online for potential values.
Once that's done, your choices are to either sell them online, here or elsewhere, or keep them for your heirs, or other family members.
The goal is to know what you have and what they are worth in today's economy. I cannot stress the importance of that enough. I know it's a bit of a bother to do the work, but the payoff is knowing the values of what cards you have, if nothing else.
You may find your collection is valuable enough to warrant insurance, through your home or rental policy, for example. In that scenario, your insurance company will need a thorough list of all cards and values, so you would be covered for any loss.
Of course, if you decide to sell, we'd LOVE you to post them here first, pics and descriptions, please!