In terms of marketcap decrease it's by far the largest but I agree that shouldn't be the only measure of what constitute's the biggest bubble.
What matters is
price. It seems like price growth in percentage terms ought to be the defining factor for bubble magnitude. That actually gives us meaningful information to distinguish between bubble cycles.
Total market cap completely distorts things because it's a function of total supply (for all coins). The majority of supply is never traded on the market and therefore shouldn't be factored into "growth." We're talking about lost coins, inactive coins, and especially large pre-mines and token issuer holdings. Using these as huge multipliers for price really exaggerates the total value of the market to the point where the numbers are useless.
Which bubble was largest depends where you measure the bottom from. 2011 appears significantly larger than 2013, which appears significantly larger than 2017. Each bubble seems to be getting smaller in terms of relative growth.