I've seen this question pop up now and then. My first warbird was a Spitfire with all the gear. Retracts, flaps, etc. Was a harsh learning curve but I've managed to keep the plane alive all this time. "Knocks on wood."
I always read our remarks to this question and the P-47 Thunderbolt is always mentioned as the easiest to start out with and then maybe the Zero second. Just thought it would be helpful to Scalemaster90 and anyone else to have a top five poll on the subject.
Let's keep it simple and within the limits of our hobby market. What I mean is,,, don't mention planes that aren't out yet or haven't been produced in several years. Or planes you've never even flown before. Then add a small comment afterward.
I'll start.

1. P-47 Thunderbolt (I flew a TopFlite gas version. Very easy to land which is nice for a change.)Gas
2. A6M2 Zero ( Takeoffs and landings are straight forward but it can get a bit twitchy at low speeds.) Glow
3. P-38 Lightning (Really sweet takeoffs and landings. Has one or two harsh lessons to learn in the air but besides that it's a joy.Elec
4. FW190(short nosed version) (Mine has been a real sweetheart so far. Comes in nice and slow. Not an acrobatic kite,, just scale.)Glow
5. MkII Spitfire (Need some speed on takeoff but with full flaps landings can be fairly slow. Will tip stall if too slow. Fast and agile. Gas

As you can see I didn't mention the Hurricane, P-40 ,P-51 or the Me109. I've never flown the P-51 but I have a 109 and will be building another soon. No Russian or Italian birds here either. Or bombers. Dive or otherwise.
A few friends have the Mustangs and they don't seem like a first timer plane at all. I know my 109 is not for newbies that's for sure.
I have not built any U.S. Navy planes yet either. But I bet we'll here from those guys. Very popular build.