I know what you mean about the drive from Maine to NY, I live in the Champlain Valley for 18 years now and have never made it to Katadin yet, which from what I hear about it, is debatably the most spectacular mountain in the east. In fact, the only Maine mountain I have ever hiked is Bigelow. It is real tough to drive right by the Whites when I have already been driving for close to 3 hours. One thing unique to the Adirondacks is the slide climbs. My favorite hikes in the east are either Huntington Ravine ascent of Washington with Boote Spur descent, or Colden Dike ascent with colden east slide descent in the ADKs. So you can guess what my choice for an ADK hike would be if I could only do one hike in the ADKs. You should be experienced with off trail travel to do the dike and the east slide is tough to find from the summit ridge trail, but trust me, it is there. Also, the dike ascent loses allot of its luster if you get out of the dike to late and miss the open slide ascent. It is also a hike I will only do in dry conditions. Other spectacular hikes - Rocky peak & Giant traverse with 2 cars, 1 at each trail head. Haystack for summit view, Saddleback for fun west face scramble (plus you can contrast Saddlebacks, Maine vs NY), Basin, Gothics (probably the best mountain to look at from afar, which is the problem with its summit view, you can't view gothics itself). If you go to Gothics, go to Pyramid peak, outstanding viewpoint of the slides !!! Algonquin is gorgeous but crowded due to its proximity to the trailhead, Iroquois on the same ridge is probaby more picked a favorite since its summit view is similar to Algonquin but it is a couple miles further from the trail head then Algonquin, most day hikers stop at Algonquin.
Non 46ers favorites: Noonmark, Hurricane, Tongue Mountain at Lake George.
And it goes on and on and I better get back to work...