The Dingoo is nice and was innovative at its time, but it doesn't live up to modern standards. It can't run anything more intensive than a SNES game, and it lacks support for any modern games (being a proprietary system and all).
I still hold my opinion that you can get the best bang-for-buck by buying a cheap phone and a controller. Even if in a couple of years you aren't satisfied with that phone anymore and want to emulate, let's say, GameCube titles - you can still transfer the controller you have, and you'll have basically the same experience. It just makes financial sense, seeing as Android consoles are very expensive compared to phones because they target a niche market, and an Android console will probably be outdated within 3 years anyhow.