I have a 2000 Odyssey and get about 18 to 19 in town, 25 highway.  Something
ain't right with yours.

You are driving a 5000 pound hunk of steel with a 240 hp engine. You aren't
going to get any better unless you monitor your driving habits very closely.
Around town can vary considerably, stop and go every 500 feet, hills, it
changes consumption considerably. My 04 will vary from 12 in the city in the
WVa hills to 27 on the flat freeways in Florida. All it takes to drop
several mpg on a tank of gas is one or two 'gotta beat that sucker' from the
light. If you want to read what others are getting look at the forum at
www.odyclub.com.
  You really need to learn haw EPA mileage is calculated. It was never
meant to state what you will get on a particular vehicle. It is a set of
standard driving conditions that all cars are judged by so they can be
compared. Heavy vehicles with big engines will always get less unless you
are driving it to the same standard driving conditions.

I have 2000 Odyssey EX and around town we are getting 22. We have had trips
from Boston to Gettysburg around 33MPG with premium and cruise control.