Enough leg room is relative, I'm just under 6'4 and I have very long legs, my torso on the other hand is not as long. So, the lack of legroom in the 4Runners is very much evident to me.
I tested the 4th Gen and the 5th Gen over a period of a month.
The 5th Gen has the same amount of legroom (IMO) when compared to the 4th Gen. However, somehow, the dimensions and sitting position on the 5th is slightly better and you feel just a little less like you are sitting on your ass with the legs folded above you.
The seat on the 4Runner the pan is longer slightly on the 5th gen, which means if you have long legs, your legs will get just that little bit more support when sitting. Compared to the Explorer, Grand Cherokee and even the Pilot,it is severely lacking.
Keep those legs active and stop often if you want to avoid the blood clotting