Clueless Mom
I can in no way recommend the Lionel G gauge Polar Express set. It is not a good quality starter set. If you are interested in G gauge there are better alternatives.
An O gauge starter set was a very popular Christmas present for young boys decades ago and it is still a great gift for many of the same reasons: O gauge is a good size for young hands and O gauge trains tend to be ruggedly constructed.
The O gauge Lionel Polar Express set you linked to would likely be your best choice and a good value if the Polar Express movie connection is a prime motivator this Christmas. The set comes with Lionel's fastrack. This is a popular track system. It is easy to set up and take apart and a wide variety of track sections and switches are available if you would like to help your child expand their layout in the years ahead. Fastrack is noisy, especially if set up an a hard surface. The noise level should be acceptable on carpet under the tree or in your child's bedroom. Lionel Fastrack will work well with nearly all other brands of O gauge trains. The transformer included in the set, the CW-80, is Lionel's standard train set transformer. It will run all Lionel trains and many other brands although it is not recommended by MTH for use with their trains.
If your budget has some room above the Amazon price for the Polar Express set and having a PE train isn't your top priority I would agree with the other posters that an MTH train set is well worth considering. MTH is based in Maryland and has grown to become one of the worlds most innovative model train companies. Twenty years ago MTH made top of the line trains for Lionel. Today they make their own line of G, HO and O gauge trains under the MTH name and make reproductions of 1920s and 1930s vintage trains under the Lionel Corporation trademark.
MTH train sets come with quality transformers that will operate all brands of trains. The track in MTH train sets is more difficult to set up and disconnect compared to Lionel's Fastrack but it is quieter. The cars in MTH train sets come with diecast metal trucks and couplers and tend to be more ruggedly built than the cars in Lionel sets.
MTH train set locomotives equipped with ProtoSound 2 or ProtoSound 3 have the best quality sound and smoke available in an O gauge starter set and offer full remote control capability. The sounds are based on digital recordings and are very authentic. In addition to a whistle and bell the chuffing sound of a steam locomotive is synchronized with the smoke from the stack. There is an off switch for the smoke and a volume control for the sound. Diesel sounds from ProtoSound 2 or ProtoSound 3 are very realistic as well. If you buy a train set with ProtoSound 2 or 3 you are getting the same quality electronics that MTH puts in their top of the line locomotives.
Some MTH train sets come with the DCS (Digital Command System) Remote Commander, a simple hand held remote control. All train set locomotives with Protosound 2 or 3 can be operated with the MTH DCS set that includes the full featured remote control. If your child develops a deep interest in trains and builds a permanent layout the DCS set would make a wonderful gift for a future Christmas or birthday. This past October MTH also announced that they would be offering a free app in 2013 to allow remote control of their trains through iPhones via home wifi and the DCS set hardware.
Amazon has a very attractive price on the Lionel Polar Express set. If you are considering a MTH set you might want to call or visit a local hobby shop. MTH has a list of their authorized service centers. Many of them also sell Lionel trains so you might be able to comparison shop.
http://www.mthtrains.com/categ...ized-service-centers
Ask the gang here any more questions you might have. In addition to a bunch of kids at heart and a few actual kids there are train shop owners and repair technicians who keep an eye on the forum. You are likely to get a bunch of technical help if you need it. All of it will be free and most of it will be worth more than you paid for it.
If you have any questions on Christmas feel free to ask. My brother Dave has a tradition of starting a thread on the three rail forum for any of Santa's helpers needing emergency assistance.
Good luck shopping and have a Merry Christmas.