Using Latex forces left-alignment of lines in cell array of strings . (This may have been changed in the newest versions of Matlab. I use 2014b.) I think you can get most (or all) the effects you need by using the standard Tex formatting, which will center both lines. Example:
str1 = sprintf('\\gamma = %3.1f',1.4);
str2 = sprintf('s_k=%d, a_k=%d',2,3)
figure;title({str1,str2});
