Easiest Pokemon League

Johto in terms of level, Unova in terms of type. With Johto, I usually win on my test run and I can beat Unova with a Bug type, Flying type and Dragon type.

Johto was easiest by far. They were significantly under levelled and their types were incredibly easy to counter - I didn't find them to be at all challenging to beat. Koga was a nice addition to the Johto league but even with their new line-up I found them incredibly easy. I'd wager it has something to do with Johto being a great region for training in though; things seem to level up a lot faster there than other regions.

Playing nowadays with my experience, I don't find any of them hard anymore. So basing this off initial playthroughs, I'm going to say Unova 2's league was really easy, even the champion. I went through without losing anyone my first time playing Black 2, and I couldn't even read the game. Then again, it only came out last year and I was 20, so I knew what I was doing at least.

Emerald (not RS) was pretty easy too. They gave you access to a level 70 Rayquaza, so if you really wanted to, you could blaze through there. ~_~ I only brought it with me once, and even still, I kept Ray in reserve really. Didn't need to use him but one time, if memory serves. lol

I'd have to say the original Red/Blue has the easiest E4. Sure, they may have higher levels, but the pokemon tend to waste turns using crap like Agility or using Super Potions when it's not going to do anything. It's actually possible to beat the R/B E4 with pretty much the same levels that you'd use against G/S/C's E4.

I can't really agree that Johto's E4 is easiest because of the levels. While they are a lot lower than the other regions... so are you (unless you spend hours grinding). I find that the better AI makes up for the levels anyways. Still pretty easy, but they can actually do some damage if you're not careful.

I've always felt that the E4 difficulty goes up with each generation with the exception of a slight dip in Unova compared to Sinnoh.