Well Mike Tyson, Evander Holyfield and Vitali Klitsco were not tomato cans. Each was a legitimate Heavyweight Champion in their own right in slightly different periods.
Mike Tyson is quoted as saying "I never could have beaten Lennox, not on any day".
Of course Lennox's idol was Ali, that's who he wanted to be like, so even in promoting Lennox as a great you do get back to Ali's legend.
Hasim Rahman, David Tua and Tommy Morrison, all of whom Lewis beat, were the equal of many of Ali's second tier of opponents.
Tyson is the only one on that list to deserve to be in the same sentence as Ali, Frasier and Foreman. The rest, including Lewis frankly, are also rans in boxing history.