What Tobes said really makes a lot of sense.
Mac hardware is somewhat overpriced to keep their software prices low - example, you can buy a Mac OS X Snow Leopard 5 station upgrade pack from Apple direct for $49. A single upgrade licence for Windows Vista to Windows 7 is going to cost you about £120 if you buy it direct from Microsoft. You can expect the next generations of Mac OS X and Windows upgrades to be similarly priced, however, you're going to spend a significant proportion more on the hardware if it's a Mac unless you're buying a seriously 'weapons grade' PC.
At the end of the day it comes down to budget... you're barely going to get a Mac at all if your budget is, say, £500 - it will be secondhand. You could get an entire PC system, including printer and a limited software bundle for that which will easily see you right for the next 4 or even 5 years.
There are precious few things a PC can do which a Mac cannot, but gaming is one thing Macs fall down on. Older games can be run in a virtual machine running Windows on a Mac, but for more up to date stuff, particularly where high end graphics adapters are required, that just won't cut it. You'll still need a Windows licence to run it in a VM, usually it will install OK if you have the product code from your old PC, but not always.
Even if you're a computing novice and the majority of what you'll use your home computer for is web browsing and email, with a few office type documents now and then, don't ignore the various Linux distributions as a genuine possibility for you. The only real drawback with Linux is the relative scarcity of people able to support you on a commercial basis should anything go wrong. However, the web community is vast, so it's not impossible to get free support for your free operating system provided you don't mind doing a little research and pressing some buttons yourself. As the operating system is free you can frequently save £70 to £80 on the price of the same hardware by not buying the bundled Windows licence.
In short:
Low budget: Intel Atom based netbox and monitor with linux OS and a compatible printer - in the order of £320
Medium budget: AMD based PC with Win7 £500-£600
High budget: Macs start at around £800 and for a top flight one can exceed £2k
You pay your money... especially with a Mac
Cheers,