Emulation can't compare to the real thing. Either accuracy issues, not using the real controller, or picture and sound differences tend to bother me with emulation. Though it's better than going without playing great classic games at all.
No doubt. I hear you, though after getting a USB saturn pad, the controller issue is a lot less of an issue for me now.
The emulation inaccuracies are still there, and for some systems, I couldn't think of replacing the real hardware due to these inaccuracies (Sega Saturn for one), but for most 8 & 16 bit systems, it's getting to the point where it's
starting to become a viable alternative to real hardware for me. Especially when I have too many systems taking up shelf space with 50,000 different wires running behind the TV.
Software, on the other hand, I'll still purchase the ones I like as long as it's practical (that is, it doesn't go for crazy sums), as I like having a physical copy with manual, maps, and all that (That's even for cartridge/card software).