wow those are some great informative solutions to my problem, thanks guys.
I own a:
-Atari 2600
-NES
-Sega Master System
-SNES
-Sega Genesis
-N64
-Sega Saturn
-Playstation
-Gamecube
-Dreamcast
-PS2
-Wii
and In the future Id like to hopefully get me a PS3, Xbox 360 and maybe a Sega CD
What inputs does your Tv have? Or do you possibly even own an AV Receiver where you could loop multiple inputs through one output?
I ask because some of these consoles have different ways to hook them up. You could connect your Dreamcast via SCART or VGA (using the VGA box), The PS2 and Wii via SCART or YUV. I'd recommend YUV for the Wii as it provides you the best picture you can get out of that system.
The Atari 2600, NES and Master System can all be hooked up via the coaxial cable supplied with the console. There are SCART cables for at least the NES but they're pricy and, lets be honest, it's not worth it for the graphics.
The SNES, Genesis, Saturn, Gamecube, PS1, PS2 and Dreamcast are best connected via RGB SCART cables. You can connect the PS2 via YUV if you want, but in my personal oppinion there's not much difference and the YUV cable is more expensive. Basically a matter of taste. Same with the Dreamcast, you could get the VGA box and hook up the Dreamcast via VGA. It does provide you with a pretty good picture but the VGA box is pricy and your Tv must have a VGA input.
Since the N64 doesn't provide a true RGB signal without modding the hardware you can use the composite cable that came with the smoke projector, err, I mean console

The PS3 and Xbox360 are best connected via HDMI. If you have a newer AV Receiver you can connect them via HDMI to the receiver and loop the PS3's and Xbox360's signal through the HDMI OUT of your receiver. That way you get the best picture and digital sound. In case of the PS3 Slim you even get 7.1 DTS HD, DOLBY TRUE HD and DOLBY DIGITAL PLUS sound instead of "just" DOLBY DIGITAL 5.1 sound. Additionally you could hook up the Xbox360 via YUV (a YUV cable comes with the console) or VGA.
The Sega CD is connected to your Genesis as far as I know, so it will use the output of your Genesis for picture and sound.
You see, there are plenty of ways to connect these consoles to your tv/receiver/beamer/whatever you have
