Lately, the Rhodes/Shield feud has made me emotionally invested. When The Shield came out to attack Dusty that first time, I literally said "Oh, no!" while sitting on my couch. And when Dusty was cutting promos I felt the same way. Especially the huckleberry line. THEN, they beat The Shield and got their jobs back and I felt like I was 5 years old again. The stuff with Bryan/HHH/Orton has me invested, but not nearly to the same level.
It's pretty rare that I feel like that, but I love it when I do. Previous to that, it was probably Aries winning the TNA title last year. Basically for me, I know I'm emotionally invested when I really care who is winning a match.