As others have remarked: need more info to better comply with your request.
Overall, it would probably be Apple, but it's a very limited company, certainly compared to the sprawling lines of HP and Dell. You can buy only a handful of models, which are what Steve wants, not necessarily what customers want (xMac?). They have the best design, sometimes the best construction, and almost inevitably the best support. However, if you drill down through surveys, you'll note that reliability isn't that much better than many PC brands -- it's just that if something does go wrong, their support is rated as markedly superior.
But to reiterate: there are many categories of systems (gaming machines being perhaps the most prominent) that simply don't exist within the Apple ecosphere.