Top 5:
World League in principle was a fantastic idea. Great to play Super 15 teams against Magners League teams for example.
Inclusion of many lower-tier nations' international teams.
The sidestep, fend and shoulder barge animations. Much better than the early Rugby League games, for example, where people would just sidestep and slide through the line jerkily.
The addition of the offload, and the set plays.
The ability to play multiple players on the same team makes for a great time!
Bottom 5:
Time and time again it's come up: lack of consistent and well-researched stats. I know this is tricky to get right, but some of the players just smack of no effort. Lachlan Turner was a new addition to Rugby 08 with a speed in the 40s!!! All of his stats just didn't seem to be updated. This also includes the special stats like tackle breaker etc. (e.g. Ryan Kankowski's only special skill is tactical kicking!), and the preferred positions (again, Kankowski is Flanker, Number Eight or Fly Half!). This is frustrating when you try and move backs around in the backline and a fullback can't play on the wing or centre for example. Not to mention the lack of licences for some players (eg. French players, Yannick Jauzion/Jezebel!)
Can't add created players into the World League/Career Mode in Rugby 08.
Predictable AI meant that you didn't really have to play proper rugby and could just exploit the same gaps/deficiencies every time.
A general half-heartedness in the stats, teams and leagues. Lack of inclusion of many provincial competitions (only included some Top 14 teams, some Magners League teams, no Currie Cup or NPC. If these were really polished the game really could be absolutely fantastic!
Gameplay/Controls: No easy way to chip and chase, long kicking animation takes too long so you often get tackled and drop the ball; some set plays are useless because the animation takes so long the AI defenders arrive and tackle the 5/8; scrums and lineouts jerky/predictable and seemingly random turnovers at rucks.
I may sound harsh with my criticisms, but don't get me wrong. I LOVED these games. I have probably played over 20,000 hours of rugby 08 over the last 4 years. These tweaks and additions could turn an enjoyable experience into a phenomenal one, with great lastability and gameplay.