Yes, the basics are pretty much the same as for the 8-/16-bit systems. Some things are easier, some are more difficult.
I can't speak for the Sega Saturn, but many PlayStation games use the standard ISO9660 file system. File names and the directory tree provide important clues about the content and structure of the game's data. Furthermore, there is a bunch of common file formats (e.g. TIM) that additionally ease reverse engineering.
Another advantage of this is that you usually don't have space problems in the same way you would have with traditional cartridge-based systems because you can almost arbitrarily resize the files. This is of course limited by RAM space because everything has to be loaded to memory before it can be used. Hence reading from the CD-ROM is another bottleneck and a lot of data is compressed to reduce reading times.
(The next paragraphs apply if you want to do advanced hacking, i.e. related to assembly.)
Reading disassembly for the newer systems can, however, be a daunting task, due to the shift in development from assembly to C or C++ (especially the latter can lead to obscure assembly code). Still, there are many firmware and library functions that are shared among games and if you can identify these it helps a lot (e.g. LoadImage).
Most other things are the same in principle, just know your hardware. For the PlayStation, understand the VRAM and how data gets transferred into it, understand how the game can communicate with the GPU, and so on. For example, finding the routine responsible for rendering text follows the same process as for older systems: Look how the text gets rendered (e.g. textured quads), find out how the game gets these into VRAM (e.g. DMA), and where the game gets the values from the storage medium (= CD-ROM). A good debugger (e.g. no$psx) will help a great lot here.
Anyway, there are more experienced PlayStation and Saturn hackers around here, so maybe they can give more detailed explanations and tips.