lol Yeah, I also tried that. The right angle edge of the 3" looks weird resting on the angled edge of the 2~4 piece. Plus, I'd have to figure out some way to get the 2" part to stay in place inside the 3" part, all the while trying to make the whole thing not look crappy. I'm right there with you though. With the available pieces of PVC they had there, I think what I ended up with is about as good as it gets.
Of course, PL1 could pop in here and whip out his linktionary and show me that I've ---fouled up beyond all recognition--- up, so... there we are. 
To center the 2" in the 3", you can use a
reducer bushing or concentric holesaw holes in wood.
First use the one that fits the 3", then the one for the 2".

To angle the base pipe to mate better with the 2" - 4" adapter, make a router jig like below.
It is made of 1/8" hardboard (white) and two pieces of 1" x 4" forming a 90 degree angle.
The 1" x 4" with the pencil line is not connected to the jig.
For your jig, make a hole for the bit in the "Trim on the inside" position.
Position the bit to angle/trim the inside of the pipe, leaving a small area un-trimmed as you press the pipe into the 90 degree angle and turn it.
Once it is properly trimmed, you should be able to glue the 2" - 4" adapter in place.
Scott