Well, tehnically, one could play some games without owning the console through the help of emulators. Emulators by themselves are not illegal, so they are a completely legitimate way of playing the games you own.
Having said that, if you want to consider yourself a legally legitimate customer (which you probably do if you buy all your games), you need to buy the appropriate console. Afterall, if you don't, you are (in a sense) cheating the hardware manufacturer of his money (unless they no longer produce the console; in that case, it's a moot point).
Besides, emulators for certain systems require you to extract the BIOS from your console to work to begin with. Plus, it is still handy to have the actual console (even if you don't intend to use it much) in case your PC breaks down or you want to travel somewhere.