I like this one too... there's a bit of road riding (I recommend veering off and visiting some wineries rather than following Lakeshore the whole way) but it's mostly trail. Inn at Lock 7 is a good stop along the canal side, and of course Niagara-on-the-Lake and Niagara Falls have their charm.
http://www.niagararegion.ca/governme...gncr-maps.aspx
About 100miles for the loop, with some side trips possible.