BSP is acutally just another scene management. It just sorts things out for rendering. The way it is done in GS with automatic portal generation is easy for the user but generates way too much portals and thus it calculates very very long for bigger levels.

The lighting of blocks in GS is another quite old and weak point. Light-mapping is not always the best way to go. It is perfect for flat surfaces, simple walls and floors. But the more polygons you get the worse it becomes. You will have lots of artefacts and you need high resolution maps.

If you use models with more polygons (and this is the norm with todays hardware), then it is quite useless. Then it is better to use vertex lighting since you have enough vertices in such a model. It still is static lighting, but ist not limited to texture space, so it makes less trouble and uses less memory.

Many commercial engines and some indie engines (like Torque and C4) can support both and render your world with a mixture of lightmaps, vertex lighting and real-time lighting. Because each of them have advantages and disadvantages.

You cannot beat such a mixture of technologies with the old-school block level lighting.