Which Android apps take up the most memory?

I must be honest, I am quite disappointed with my MyTouch w/Android. My relationship with the smartphone started out quite well as I finally gained pseudo iPhone social status and the admiration of all my friends. However over time the phone has become slower and slower. I love the fact that Android allows you to run multiple apps at once (which the iPhone does not allow, or so I’ve been told), but this has proven to slow the phone down immensely, to the extent that I now cannot exit an app fast enough to make a phone call right when I actually want to. This has resulted in, I will admit, infuriating wait times (2–3 minutes, and I do consider myself a rather patient person) for the dialer to open, after first opening Taskiller and manually shutting down the 2–3 background apps running. If there was an ever emergency, I don’t want to get stuck in a situation where I can’t make calls. I’m sorry, I know it’s great to have mobile internet and Pandora, but I got the phone to use primarily as a (gasp) phone and it’s getting to the point I’m questioning whether Android is truly an iPhone killer. My iPhone-wielding friends have gladly proven to me that their one-app-at-a-time device fluidly and effortlessly transitions between apps, and there are no wait times waiting for the dialer to open.

My question is, then, now that I’m stuck with the MyTouch for two years, which apps take up more memory (RAM?) than others? Because I want to get rid of those apps.