I've found this post on Nikkei's Trendy Net and am totally translating ripping it. (what's up with their awful article pagination!)

First up: am/pm with its シャンティ・オ・フレーズ Chanter aux Fraises (2,500¥)

Then CircleKSunkus' シェリエドルチェ クリスマス苺サンド  Cherie Dolce Sandwiched Xmas Strawberries (3,400¥)

7-11's かまくら Snow Hut (2,100¥)
No strawberries, you ask? They're inside!

Daily Yamazaki's スウィートシェアリング Sweet Sharing (1,800¥)

Family Mart's レ・アントルメ国立クリームストロベリー L'entremet National Christma-Strawberry (2,500¥)

Mini Stop's ベルギーチョコレート・ノエル Belgium Chocolate Noël (2,800¥)
No strawberries?! How courageous of Mini Stop.

And finally, Lawson's 苺のショートケーキ Strawberry Short Cake (2,800¥)

So which one is your favorite?! And could you imagine ever buying a Xmas cake from a convenience store?