As others mentioned, good leather is excellent. Other materials CAN be. But they can all also be awful. I will cite a few examples:
1. BMW high-end leather (like in my M5): Absolutely fantastic. Very thick material and has held up incredibly well. Also, the seats themselves are incredible which certainly adds to the experience.
2. Ford's leather "mix": What we've had in all three of our Expeditions. Seat sides are a vinyl, bolsters are leather, seating surface is perforated leather on the front seats. We've had a bolster tear (drivers seat). That's about it. So I can't rip on it too hard, considering it lasted almost 200,000 miles. The other seats are all fine.
Also, as noted by somebody else, these are very easy to clean. An important thing when you have three kids and a dog.
3. BMW's vinyl (like on our 328i): Junk. It cracked and flaked off and even the passenger seat was showing signs of going south. We were not impressed.
4. Chrysler's leather "mix": What's in the Charger. I have no idea if any of it is real. The inserts are supposed to be suede but.... With a fraction of the mileage that the Expedition has on it, and significantly less than the M5, the bolster on the drivers seat has already cracked. It would appear to be a similar material to what BMW used on the 3-series.
The seats themselves are fantastic. So it would have been nice if Chrysler had spent a few extra cents and used better material. These are the upgraded "Daytona" seats, so we were surprised at their lack of durability.
5. Subaru cloth: What was in the '05 Forester XT we had for a bit. Very comfortable, quality seemed good with good support. A good execution of a cloth seat.
6. Ford leather (80's): What was in my old Town Car (1989). Held up well for about 300,000Km and then started to tear on the passenger side (drivers side held up, go figure). This was the "couch" style interior with the massive leather seats with zero support.
7. Ford cloth (80's): What was in my Mustang GT. The bolstering tended to flatten out so the seat structure wasn't great. The material held up well enough but stained easily (IMHO).