I assume we're talking road bikes?

Here's the official maps (downloadable).

I had a bunch of 'fave routes posted on Routeslip, but alas, that webpage is gone (RIP). I'll have to repost them somewhere.

The Oakcreek/Cudahy/BayView part of the Oak Leaf trail will run from Grant Park north to the Coast Guard station next to the high speed ferry. Take the trail or just ride on Lake Drive ... that trail needs to be updated, but even on Lake Drive that's a good loop.

South of Grant Park you can ride a little further to Bender Park which has an excellent view of the lake before you drop the 100 ft down the switch back road to the beach/boat launch.

If the wind is out of the north east (when isn't it?), take 1st street north to downtown, then over to the lake front and there is a bike path from downtown to Silver Spring Drive along the old railroad right of way. For some speed, just take Lake Drive (different that the one on the south side) back to downtown. That's a very popular cycling route.

If we're talking MTBs, then that's a whole different ballgame.

(PS: Be careful when you say "parkside" because that's a real place on the north end of Kenosha. They used to race at "Parkside" and that may throw some people off. )