Just like everything else in a contract, the earnest money amount is negotiable. While important, I've never known a seller to say, "Well, it's a low offer, but I'll take it because they have a substantial earnest money deposit".
Also, it depends on your area. In some parts of the country, a 1-2% EMD is expected, where in others, it can be as low as $100. Bottom line is, get a knowledgeable buyers-agent to advise you on what is low enough to show your "significant interest" - don't just haphazardly throw a large amount into the transaction as there is always the possibility that the contract will go south and your EMD could get tied up.
Beware of agents who tell you, "if your loan is denied, you get your emd back". Yes, per most contracts, you get it back; however, the seller must release it. If you have tied up a seller's home for months and then have your loan denied, they may decide to tie up your EMD in return. If a seller won't release the EMD, you have to go to court to have a judge release it.