Frontierland; two side-by-side E-tickets, a great waterfront with kinetic elements (the steamship and ferries), a seamless transition into it's neighbor (to the point where I'm not entirely sure where Liberty Square officially starts), and it's all wrapped up in that overly detailed, "hyperreality" that Imagineering is known for, complete with a good smattering of rockwork. I could spend all day here (I probably spend 90% of my time at Magic Kingdom on the west side of the park actually)
Tomorrowland however, is just a mess; huge naked expanses of plain concrete, ugly lighting and speaker rigs (with dirty exposed wires! bad show!), and no coherent sense of time or place. Buzz Lightyear's bright green plastic entrance just looks cheap, and shows dirt like crazy for some reason. They need to add planters, tiered walkways, themed seating areas and return to a unified color scheme. Not to mention getting rid of the tacky garbage littering the area like the Little Green Alien souvenir stand. Tomorrowland in its current state reminds me more of a 6-flags than anything else.
After thinking about it, I think I might know why TL looks dirtier than the other parts of the park. Everywhere else has rich earth tones and lots of wooden buildings. Scuffs and dirt just blend in and look like part of the landscape. In TL, every little scratch on a metal pole stands out like a beacon. I'm not sure what the solution is for that. Disneyland tried to retheme theirs to a bronze colorscheme a few years ago, but it looked terrible. Maybe WDW should just redo the whole land in DL Paris's turn-of-the-century steampunk look. No way for most of the existing attractions to fit into that though. TDO is a bit stuck.