Each has their own use case and I think the moment of solana was last year. And as for Sui, it hasn't gotten out the full potential of it. While if it's about being the competitor directly of solana, I don't know about that since each altcoin has been made for each of their potential belief by, first its dev and secondly, by its community. If the community speaks about what's the potential of it and debating of its competition against solana, maybe it is.
SUI actually got its full bloom pretty early back when even bitcoin hasn't reached $100k.

This chart is SUI at its full bull.
I still remembered it a lot because price just went ATH multiple time and the entire ecosystem was blooming. NFT was priced high, some random memes were valued high as well, and tons of new project doing TGE with massive success.
Now, I guess we've reached the point of decline for SUI. Price doesn't look good at all