Yes, cleaning all of the dust off would almost definitely help lower your CPU temps, particularly if your CPU fan is also very dusty. Dust is a very good thermal insulator so any dust in a system is not good at all.
If you wanted to an even more thorough job you could remove the heatsink and fan unit and clean off any leftover thermal paste with isopropyl alcohol from both the heatsink and the CPU. You'll then need to re-apply thermal paste and fit the heatsink correctly in place. Google and YouTube are your friends if you want more info on this. Hope this helps and good luck!
I cleaned out the dust but that didn't really seem to do anything. It still idles at around 60 degrees and goes to around 70 when under load.
One thing I don't understand is that it considers games like Runescape 100% load. I thought a lot more demanding games like Crysis would put a heavy load on your CPU, not a Java-based game such as Runescape. These 100% spikes are causing my computer to lag, and I'm not sure if it's because of overheating or not.