 Although some reviewers initially expressed concerns about the difficulty of expanding Portal into a full sequel , Portal 2 received critical acclaim , particularly for its writing , pacing , and dark humor . The voice work of McLain , Merchant , and Simmons were also praised , as were the new gameplay elements , the challenging but surmountable learning curve , and the additional cooperative mode . Some journalists ranked Portal 2 among the best games of 2011 , and several named it their Game of the Year . Portal 2 has since been hailed as one of the greatest video games of all time . 
