Dropbox still has the best syncing app and integration, but is terrible with multiple accounts and any business use. Paper is also useless.

Box offers great controls for businesses, better API and built in workflow engine, but has crappy syncing app. Box Notes also useless.

OneDrive is just shit in every way possible and acts more like an unwanted virus in new Windows installations.

Google Drive has solid syncing with built-in search and google docs integration which is the best office suite other than MS office. Their Team Drives feature is finally doing things right for businesses, although it still has a broken permissions system and issues with desktop integration.

There's also Apple, Amazon, Egnyte, Quip, etc for other niches. Overall, we are nowhere near perfect with any service. All of these companies will continue to grow since there's no singularly great option yet.