Yep, the first one. Only took me in the region of 5-10 hours, sadly enough. Even when going back to do the goals you've skipped, the lifespan is miniscule. A shame, considering that Tony Hawk's 4 hit the perfect balance with a nice learning curve and lengthy story mode.
Still, the RPG elements put a much required new spin on things and the story itself was solid enough, if you overlook the cliched characters, dialogue and plot turns. Goals were sufficiently varied, though only challenging when they didn't make it clear what you had to do, and the "make-the-tape" tasks at the end weren't quite as good as THPS4's Pro Challenges.
Gameplay was as good as ever, except for the appalling driving missions. Off-the-board was a key addition, placing a whole new spin on the levels, but that's not to say it was an improvement. What was most impressive for me, however, was the level design. Combo-lines and densely skatable areas were seamlessly woven into believable urban environments, which benefitted from a slight graphical polish.
On the whole, it was a solidly enjoyable experience and, given that there are no close competitors, one of the best extreme sports titles to date. In essence, it's a different game to its predecessors. For me, THPS4 marked the pinnacle of the series in terms of skateboarding - it was refined and wonderfully designed in every aspect, a joy to play. With Underground, there was no logical course to follow from 4, and so they introduced the changes I noted above. These were necessary and nice, but not improvements - moreso digressions.
Which begs the question - what has THUG 2 brought to the table? I'm sceptical about buying it; I didn't feel that Underground was worth the price I payed, and considering that this is the direct sequel, nothing suggests to me that any significant improvements have been made. If anybody who's played it could write a little about it, I'd be grateful.
I've been with the series since its humble beginnings on the PSOne, and despite not having played the mobile/handheld instalments, I'd like to think I have a fairly good feel for it. The new direction is interesting for me, but nothing to rival what was so nicely brought together in 4. Perhaps, by the time the Underground series is refined as much as it can (probably around THUG4), the series will take a new direction - perhaps fusing skateboarding, biking and the other extreme sports into a new style of game - Tony Hawk's Upper Mantle, if you will.
Will they ever leave the series alone? Not that I'm particularly against new twists on the gameplay, but there are only so many levels to the Earth...