Gary, who signed on a free transfer from Coventry City on Monday afternoon, feels that he is reaching the prime of his career, and says: "I wanted to take my time over this, as it was a big decision for me. I had a month or so to reflect on all the different offers after the World Cup.
"I feel I have made the right decision, and I have worked with Glenn, who also played in my position, when I was at Gillingham - so I hope to learn even more now I have signed for West Ham.
"I expect to play the best football of my career and feel that I am coming into my prime now. My best football is ahead of me.
"Fingers crossed I can learn more from Glenn, and in the next four or five years I will be coming into my best form.
"I had a reasonably successful World Cup, though it is just disappointing the way it ended. If we hadn't gone out on penalties, who knows what would have happened?
"I come to this club with a lot of confidence, and I am focused on having a good start with West Ham and I will deal with the European Championships when they start in September."
The 28-year-old central defender was linked with a number of clubs over the summer, but he says: "I am not going to say who was in for me. I had a lot of offers from abroad but I think it is best at this time that I stay in the Premiership to consolidate my position with the Ireland team and possibly get honours with them as well.
"Without sounding too blase, I had a lot of offers, fantastic offers, and I need to be in the right environment at this stage of my career - and I am sure I have made the right decision.
"I am back in the thick of it and I am delighted to have the opportunity to do so with West Ham.
"I have always admired the club. It has always been a difficult place to play and the fans here can be like an extra man for the team.
"They are very intimidating, but now I hope to be playing in front of them and having them backing me.
"But the main factor was certainly Glenn Roeder. I am also learning from Mick McCarthy, someone else who played in my position, and I learn all the time from him.
"I know Glenn is a good coach, and a couple of the lads here speak highly of him, and it is a decision I have thought long and hard about.
"I know Joe Cole well - we are from the same area of London - but I know from other people how highly he is regarded.
"I wouldn't say we are the best of buddies, but I know him and I am looking forward to working with him - it will be interesting to see just how good he is.
"If I can get close enough to him in training I hope I might be able to tackle him!"
Gary faces competition at the back from Christian Dailly, who is another friend, Ian Pearce, and Tomas Repka, but he says: "I think you need strength in depth. It is probably something West Ham didn't have last year, and now we will have it.
"There will be a lot of competition for places now. That bodes well for the club, and the days have gone when a player is going to play every game in the season.
Gary is now looking to help the Hammers into Europe, and adds: "Of course it is going to be difficult to improve on last season. It was no mean feat to finish seventh, and I don't think I am being disrespectful to say there wasn't strength in depth.
"It was a fantastic achievement, but at the same time if I thought they were happy at finishing seventh this season I wouldn't be interested in playing here.
"I want to be challenging for Europe and if we can avoid injuries, and work hard, it will be possible."
Gary has played many a game before at Upton Park, and adds: "I have some bad memories of Upton Park. I remember one game, it was a hot day in April a couple of years ago and absolutely baking.
"We lost 5-0, it was one of the toughest games I have played in, and it could possibly have been even more than five.
"We had a young team that day and it was a tough game."
Gary has joined under the Bosman ruling from first division Coventry, and says: "I wanted to show a little bit of loyalty to Coventry. I was part of the team that got relegated so I wanted to give them every opportunity to get back up.
"Ideally, I would not have gone into a World Cup season playing in the first division, but it wasn't to be.
"But I need now to be playing at the highest level, not only for my own esteem but to consolidate my position for Ireland.
"I had some great offers to leave last year but I wanted to show a little bit of loyalty to the fans at Coventry who were fantastic to me.
"I hope they do very well and they deserve to be back in the Premiership."
MD Paul Aldridge says: "We are delighted to have secured the services of another World Cup star and look forward to seeing Gary settle in."