What do these names have in common? Yeah, that's a trick question. The answer is, very little. There are some very modern names/nicknames (Lexi, Addison, Isabelle), some very classic names (George, Mark), some quite old-fashioned (Preston). They are phonologically very dissimilar--some multi-syllable, some not. Almost all of them start with different sounds, and of the three that begin with /m/, two are usually referred to by their last names instead. A few have or are nicknames, others are un-nicknamable. There's a lot of diversity in this group.
On a TV show, this doesn't matter as much, because each name is attached to a physical character who we can see and hear. But on the page, having characters who are named differently enough that the reader can grasp them is crucial. The first drive-by a reader has with your characters' names may be just a fleeting impression. So if your guys are all named "Chance," "Tristan," "Aiden," and your girls are "Madison," "Olivia," and "Katerina" your reader is going to register "modern name" and not be able to distinguish one character from the next until you've done a LOT of writing showing their different personalities. This goes doubly for names like "Tristan" and "Aiden" which are phonologically similar, both ending in [en]. If you give all of your characters single-syllable names like "Jake," "Mike," "Jess," "Kate," you're going to confuse your reader in a short space.
Naming characters is one of those super fun things that we get to do as authors. But it's very easy to name a single character without paying attention to how that name sounds against all the other names. Ideally, you get a nice mix of old and new, multi-syllable and single-syllable, nicknames and formal names, etc.
In a contemporary piece, it's likely that you'll have some characters with names that are late-twentieth and twenty-first century popular, but also some that are more traditional, and perhaps some that are very rare. Ethnicity comes into play, too--think of what happens to your physical image of a character if I tell you his name is Derek vs. Diego vs. D'Shawn. I have a WIP (Controlling the Spin) where the male lead just morphed from a Cavin to a Kevin, because there are too many "rare" names already in the cast--his daughter is "Moll", and the son of his love interest is a "Hunter." More people in the cast needed to have "normal" names, and his was an easy shift.
How it all stacks up is important. Grey's has built this stack rather nicely, with a rich stable of names to go with the very different characters on the show. It's an excellent example of what one might aim for with a cast of characters that large.