If it's broken up into a bunch of pieces that have shifted and are uneven, or if the concrete is crumbling, you should replace it.

If the concrete is just cracked but not uneven, you could probably just live with it and/or resurface it (all concrete cracks eventually).

If the top is coming off but the underlying concrete is solid (not crumbly), then you could probably scrape off the loose stuff & powerwash it and resurface it.