The gazelle is not self-conscious about it's life, and whether it's muscles are beautiful or not. It will never sense the beauty of what you're describing - from it's point of view, it will just feel fear, pain, then die.

Perhaps a higher-dimensional being would also see some beauty in our life that we cannot comprehend currently - like the gazelle can't comprehend it's Olympic flow, a human can't comprehend the long-term beauty of how they toil and work against the odds.

> whose life is better? If by better you mean, which being feels more emotion/happiness/satisfaction, it's an open question. But if better implies more progress and safety/longevity, then humans it is.