The NY side is a national park, and has all the expected greenery, trails, etc... highlight is the Cave of the Winds tour, where you get to walk down under one of the falls. Outside the park, though, not a great area - I wouldn't stay in a hotel there.
Canada side is a gaudy Vegas/AC style bonanza of kitsch, but it has the best views of the falls and hotels overlooking the falls. It also has some decent restaurant options... but a ton of chains, and everything is fairly expensive, since it's a resort town.
Go just north of there to Niagara-on-the-Lake, and there's some nicer B&Bs and smaller hotels, with great restaurants and a pretty sprawling wine country. Quieter, much more relaxed and laid back.
We did a short trip:
Day 1 - NY side national park, Cave of the Winds, Maid of the Mist... drove across the bridge and stayed in Niagara on the Lake
Day 2 - Wineries and tastings, drove down to Niagara Falls and stayed in the highest floor of Sheraton on the Falls overlooking both major waterfalls
Day 3 - Spent the day in Niagara falls Canada side and then drove home.