Market cap is the standard way to compare the size of crypto assets. A coin at $1 with 10 billion tokens in circulation ($10 billion) is far "bigger" than a coin at $500 with 1 million tokens ($500 million) — the unit price alone tells you nothing.
Watch the gap between market cap and fully diluted valuation: if most tokens are not yet in circulation, future unlocks can push the price down.
Example
A token trades at $2 with 500 million coins circulating → market cap = $1 billion.