Naturally a lightning bolt will always be better than Shock, and if I could choose which one to play in a given format, i'd choose lightning bolt any day. But unless both cards are to be played in the same format, there is really no room for comparison. Shock in T2 could be better than lightning bolt is in T1, because of the relative power it may have. When judging which card is better in the same format, the answer is usually easy. But when the comparison takes place with more than one format involved, the answer isn't clear at all, and one can't compare just between the two cards, we must compare between the relative effect each card will have on it's given format.
Tim