Nothing wrong with 20 valve 4AGEs. They're awesome for what they are. They were never designed as a high performance engine, thats what 3SGTEs, 1J's and 2J's were for.
They're a high revving engine that is a good compromise between power and economy. Someone a couple of posts back pointed out the old power-to-weight argument, and they were spot on. If AE101s and AE111s weighed a bit less, they would be a heck of a lot quicker. A 20 valve 4AGE in a light weight car is brilliant, especially with some minor mods.
They'll never be in the same class as 3SGTEs or RB26DETTs, 22Bs, as they're a 1.6 litre NA engine (unless of course you work at Speedtech

).