I know that in speech we say "the bigger the better", but is this ok in written English as there is no verb....
Except for idioms, proverbs and informal speech, all sentences do require a verb. But now a day we are explicitly using informal speech, so most of the time these things are seen as normal and hence are a part of 'modern English'. Also idioms and proverbs at times lack verbs just in order to sound more rhetorical. There is a lot of everyday stuff we say which lacks the usage of verb and is grammatically 'incomplete' but we consider them because they sound 'too obvious' and thus acceptable.
Here's an article telling how now-a-days people aren't following grammar rules and still their work is acceptable: Modern English Grammar by The University of Copenhagen, Denmark.
Also, here's a complete professional research paper for the usage of verbless sentences: THE USE OF VERBLESS SENTENCES IN ENGLISH LITERATURE.
Here's some more example of verb-less speeches: (These are grammatically incorrect but are recognised as a part of modern English.)
True, no doubt.
So far, so good.
Of course not.
Down to earth!
Can you please..
Good job. etc.
Here's detailed explaination for it's usage: Verbless Sentence (Scesis Onomaton)
Hope, this helped :)