This recent appellate case McCluskey v Gabor & Gabor,  2009 NY Slip Op 02757 Decided on April 7, 2009 Appellate Division, Second Department illustrates the difference between malpractice at the trial level and at the appellate level. 
 

At the trial level one must prove the usual :"a plaintiff must demonstrate that the attorney failed to exercise the ordinary reasonable skill and knowledge commonly possessed by a member of the legal profession’ and that the attorney’s breach of this duty proximately caused plaintiff to sustain actual and ascertainable damages" (Rudolf v Shayne, Dachs, Stanisci, Corker & Sauer, 8 NY3d 438, 442, quoting McCoy v Feinman, 99 NY2d 295, 301-302; see Noone v Stieglitz, 59 AD3d 505)."

However, at the appellate level [i.e.]  a claim that the attorneys failed to file an appeal, one must prove "that, had the attorney perfected that appeal, the appeal would have been successful, the cause of action would have been reinstated, and the plaintiff would have prevailed on that cause of action in the underlying action (see Suffolk Ave. Car Wash & Lube v Oberman, 256 AD2d 75; Saferstein v Klein, 250 AD2d 831). "

In McClusky the court dismissed legal malpractice claims: "Here, the plaintiff alleged, inter alia, that the defendants committed malpractice by failing to take an appeal in the underlying age discrimination action from so much of an order as dismissed his causes of action alleging fraud. We find, however, that, inasmuch as the causes of action alleging fraud were properly dismissed (see Kaufman v Torkan, 51 AD3d 977, 980; Weitz v Smith, 231 AD2d 518), the plaintiff cannot establish that the defendants committed malpractice by failing to take an appeal from that order (see Suffolk Ave. Car Wash & Lube v Oberman, 256 AD2d 75; Saferstein v Klein, 250 AD2d 831). "