I find the Saturn and Sega CD solution much more elegant if you ask me. You don't need to buy a memory card right off the bat if you want to save games. You're system can save them on it's own. However if you need more space or a means to transport data, you can buy a memory card. Not everyone needs the 8000 blocks the Saturns Memory card gives. For many the internal memory is more than enough. Considering this solution is what modern systems do I'd say that's proof that it wasn't a bad idea.
The average Saturn game I own uses around 6-16 blocks of space. The only ones that take up more than that are NiGHTs and Virtua Fighter 2 last I checked.