1. That's the most expensive bed I've ever seen.
→ I have never seen a more expensive bed than that
...
2. This is the best pizza I've ever tasted.
→ I have never tasted a better pizza than this.
3. He's the smartest person I've ever met.
→ I have never met a smarter person than him.
4. This is the most beautiful sunset I've ever witnessed.
→ I have never witnessed a more beautiful sunset than this.
5. That's the funniest movie I've ever watched.
→ I have never watched a funnier movie than that.