Generator leaking gas and won't start.

The float valve is leaking and flooding the engine with gas. You see external leakage but there is also plenty going into the cylinder drowning out the spark plug. Usual cause is not running the generator dry of gas prior to end of season storage. Gasoline does not completely evaporate and leaves deposits behind that both plug up the tiny jet holes that regulate gas flow through the carburetor and also prevents the needle valve from completely closing and shutting off gas flow when the float reaches the proper level. While they can be cleaned, very few mechanics actually understand carburetor function enough anymore to successfully do that and consequently replacement is the preferred course of action. If your generator does not have a gas line shutoff, you can wrap the jaws of a pair of vice grips with electrical tape so it won't cut the hose and use it to pinch the fuel line shut so you can run the generator out of gas next time and prevent this from repeating next year. An alternative strategy is to "man up" and camp all through the winter so the generator is used regularly! Something else to consider is that after fixing the carburetor issue, you really need to change the oil and filter again as it has gotten diluted by the excess gasoline that was in the cylinder and snuck it's way past the piston rings. Running the generator with gas-thinned oil will ruin the bearings.