For playing games I always use my A1200. As rattus says it is there so why not use it ? Hard drives are as cheap as chips and now that WINXP allows you to simply place the Amiga HD in your PC and copy everything across using WinUAE transferng large amounts of data is pretty straight forward. However if you wanted to use you Amiga for heavy stuff like surfing the web etc then the costs to beef up a standard A1200 for example are prohibitive, and you are risking the odd short-circuit or duff power supply that could destroy that precious Blizzard!
When I think of the time and money I've spent over the years on bits and bobs for expanding my A1200 to not really get anywhere other than playing games on it, it does seem a gigantic waste of time but hey it's fun! And what the hell did I buy that A2000 for? And that A500? And that.....etc. etc.
It's shame so much snobbery seems to be associated with owning 'The Real Thing' but unless you have the time, space and money to buy a real Amiga, emulation is a great and in many ways better alternative. I've never really used emulation for anything else but testing harddrive set-ups etc.