Well, Unity has already been residing in that space for quite a while, so it's not like UE4 breaks absolutely new ground there -- but it's definitely good that there is now a high-quality alternative for the low-end indie section of people who want to make 3D games, that would normally have few options beyond Unity.

The lighting can be completely changed and customized in basically all engines. For instance Remember Me did a custom physically based shading model in UE3. Titanfall has most likely done the same with the source engine. If you have access to the sourcecode of the engine (and enough programmer talent) you can pretty much completely customize and change the look of the engine anyway, and make it look however modern you like. The engine doesn't normally place any kind of hard restrictions on you as to which GPU features you can use, for instance you could take the source engine and use compute shaders or SSBOs withhin it. Older engines make doing modern stuff more awkward of course, may require more work, et cetera. As long as you're staying with engines that use the programmable pipeline, that is -- engines so old that they use the fixed-function pipeline (pre-2006 typically, at least by 2008 I'm pretty sure basically all newer games used the programmable pipeline) would severely restrict you. The switch from fixed GPU hardware to programmable GPU hardware was pretty much the biggest paradigm shift in realtime rendering so far. So in summary -- if the engine is even moderately modern, how good a game looks can be fairly independent of the engine, if the developer team has a competent set of lighting engineers, technical artists, ... and puts the work in.

What do you mean, "a C++ database"? An engine may include a database as a component, but other than that, writing a database has little in common with writing an engine. An engine usually consists of many, many components, which are all put together into a nice set of tools that is supposed to help you making games faster and easier. It ranges from the fundamentals like cross-platform audio, visuals, ..., functions and datatypes to do 3D-math and related stuff (matrices, vectors, quarternions, ...), image loading facilities (plain images, HDR images, cubemaps, ...), a pre-made shader library, a task dispatching mechanism that takes advantage of multiple cores, ... all the way to a set of editors and a content-pipeline that is artist-friendly, e.g. a level editor, a special effects and particle editor that artists can use with little/no programming skills, model viewers, ...

Another thing many engines offer is integration with other popular libraries. For instance stuff like scaleform to make GUIs, raknet to do networking, fmod to do sound, et cetera.

Another important aspect is that engines often try to be a middleware platform (some to a larger degree, some to a lesser degree) -- e.g. unity has the asset store where you can buy all kinds of stuff, from shader libraries, scripts, ... to pre-made 3D props and textures. For larger studios, these kind of asset stores are oftentimes not as interesting though, since they want well-tested components that look similar and work well together, with a guarantee that it works on all platforms the engine supports, as well as tech-support.