There are so many places it's hard to recommend something.
But my family used to vacation in the Colo. Springs area in the early 70's and there are some wonderful tourist/vacation spots there. We would also go up to Denver. The "outdoors" stuff isn't quite as nice, IMHO, but it has some pretty nice "big city" things to do, museums, zoo, etc.
The middle park area of Breckenridge, Fairplay and south is a wonderful place to, I'm sure. I've only passed through it once 20+ yrs ago. I think this area personifies what people picture Colo. to be. High country pastures and meadows with higher snow capped peaks in the back ground.
Further north the Estes Park area with Rocky Mountain National Park is a great outdoors getaway spot. But I've never been there.
My favorite vacation spot is Ouray, in the southwest corner. It's pronounce "YOU ray". An old gold mining town nestled amongst high peaks. It's often called "Little Switzerland". For a little town of around 600 people they have 3 or 4 or 5 Jeep rental places. Rent a Jeep and explore the high country on your own. Or take one of there tours. My best friend is from there and has two brothers that live there. One of them bulldozes the snow off Imogene Pass. This is the pass that takes you over the mountains to Telluride. Better be an experienced 4wheeler for it though, it's a tough pass. But there is some breathtaking areas around Ouray. Yankeeboy Basin is phenomenal.
You can do whitewater rafting in the Glenwood Canyon and Asspain is just another 45min. up the road. Glenwood Springs is home of the largest naturally heat hot springs pool in the country. But I prefer the hot springs pool in Ouray.
I do think you'll have a good time where ever you go, but if you drop into the Glenwood Springs area give me a shout. I live just down the road.