The Keil compiler generates the following:

   1          unsigned char r1,r2;
   2          
   3          void junk (void)
   4          {
   5   1      r1 = r1 > r2;
   6   1      }
   7          

ASSEMBLY LISTING OF GENERATED OBJECT CODE


             ; FUNCTION junk (BEGIN)
                                           ; SOURCE LINE # 3
                                           ; SOURCE LINE # 4
                                           ; SOURCE LINE # 5
0000 E500        R     MOV     A,r1
0002 D3                SETB    C
0003 9500        R     SUBB    A,r2
0005 7F00              MOV     R7,#00H
0007 4002              JC      ?C0001
0009 7F01              MOV     R7,#01H
000B         ?C0001:
000B         ?C0002:
000B 8F00        R     MOV     r1,R7
                                           ; SOURCE LINE # 6
000D 22                RET     
             ; FUNCTION junk (END)

As you can see, the only values possible are 0 and 1.

The ANSI/ISO C standard is pretty specific about the result of a comparison being 0 or 1.

Jon