As far as user ratings and opinion goes, Lenovo Thinkcentre M Series, though a very fast system might not be the best for gaming. Instead Lenovo Y series, say Y50, Y510P are the two which give a very good feedback as gaming laptops.
Among other laptops:
ASUS ROG G750JX,
MSI GE60 2PE,
HP Envy 15-k006tx,
HP Pavilion 15-p045TX,
Dell Inspiron 3542, and
Acer E1-572G are the best.
Among the Best Gaming Desktops, the best user ratings go to the following:
Acer Aspire Revo AR3700-U3002,
Mini ITX-ME130JRI501-High Performance Gaming PC
Mini ITX - ME120JRA301- High Performance Gaming Rig
Hope you get one of them to suit your purpose.