Agreed; for that generation of games, they were pretty bad. It's probably not so bad for the average gamer who probably has never ridden before but anyone who's into horses is going to be able to tell. The best horses are in Red Dead Redemption as far as I'm concerned; they behave like horses would- able to turn in place, they get tired after a long sprint (but can canter w/out losing speed)- I'm pretty sure they won't just jump up or down anything ridiculous like a mountainside or cliff, but it has been a while so...there's that to consider. I may be misremembering.
2nd best would be Assassin's Creed 1- only the first one; the few moments I got up on one in 2, Brotherhood or Revelations and they felt 'dead'; made most of the right noises and were decently fast but nothing grabbed me like in the first one. Can't speak for 3 or 4- 3, I only played like 8 hours and weirdly, I did not enjoy it at all. So I never actually got to ride; and 4, well, I got it for Christmas but haven't been able to play it before now, and can't now due to the tv dying on me.