I'd second the recommendation of Flattop/Hallets. If you're just getting into hiking, on the way up Flattop gives you more tantalizing rewards of what you're going to see than does Twin Sisters...with is longer and forested for a large stretch. So, I think Flattop is a more "encouraging" hike than many others, including Deer Mtn or Estes Cone.
But if you're doing hikes in the Estes area (and elevation) with some frequency, you're quickly going to get the Iowa out of your lungs pretty quickly be trained up to take on longer and higher hikes. One of my favorite relatively short loop hikes is Flattop-Hallets then scoot behind Otis and glissade/snowball fight your way down Andrew's glacier and return back to Bear Lake TH. When I used to do this in the 80s, the glacier was safe -- always check with a ranger, however, to make sure it hasn't developed any dangers.
"Gentlemen, you are piling up a heritage of conflict and litigation over water rights, for there is not sufficient water to supply the land." - John Wesley Powell, 1883