I like coretemp mainly for its simplicity and small size, but it gives bogus readings on one of the computers I have to deal with whereas speedfan seems to work always (of course, I'm not the world). Speedfan is really handy with all the cool things that come with it, but it's a bit "cluttered" for just plain temperature monitoring.
I recommend Speccy. It not only give readings of your CPU temp, but RAM info, GPU temp, motherboard, monitor, anything and everything. But there's no function to see your highest recorded temp. I've never seen my CPU above 35c so I have no need for that. I have GPU-z for temp monitoring.